GisMap

11/18/2021

General: Information Systems/Example of a production company and General description

11/18/2021

General: Information Systems/Example of a production company and General description

Example of a production company.

The information systems are declined according to the nature of the information which they manage and according to the use which is made of it:

*that can concern the activities of a company or an administration or the technical data of a laboratory or the elements of documentation of an information center.

*The organization of data can be realized in many ways and take many forms.

*The realization of such a system must meet the needs of the users and its implementation requires the adoption of an approach that will allow defining precisely its characteristics so that the expected functionalities exist.

*An accounting-invoicing application will not the same audience and will not require the same organization, nor the same information as an information as a production follow-up application.

Even if these two types of applications

sometimes share common data.

*They can also be declined in a single system managing all the information in a centralized way or

in several practically independent sub-systems that may have gateways.

*The degree of sophistication varies from one system to another depending on the needs

and resources of each one.

In the case of a company, for example, all departments handle information:

1) the purchasing department;

2) the production department ;

3) the sales department;

4) the personnel department;

5) the support departments.

Each department manages several information flows:

internal to the department for its own operation, internal to the company but external to the department when it is a question of exchanges with other departments

and strictly external when this flow leaves the company:

with customers, suppliers, and banks for example.

The data strictly internal to the department only depend on its own organization, while the other types of data must take into account the constraints of other related to the other parties involved.

The purchasing department is thus concerned about exchanges between internal departments for requests, and suppliers and banks for responses. In order to function, it is necessary to have access to all the information concerning these exchanges.

In this way, This is how it builds up its own information system. It needs a minimum of data to trigger operations such as a request from another department and creates its own information for suppliers in the form of information to suppliers in the form of purchase orders.

The data that it for its own needs, for example, to trigger an action, is referred to as input data and the data it and the data it creates is called output data.

It must also provide reports summary reports to the company's managers, reports obtained by synthesizing the elementary information that he has manipulated to carry out his missions.

These statements can be calculated by the service itself and be transmitted in one form or another to the requesting parties, but they can also be directly available if the latter has access to the data.

It thus participates in the information system of the company by enriching the description of its functioning.

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General description

The constitution of an information system requires a thorough reflection in order to meet the expectations of future possible to the expectations of future users.

For this reason, we must distinguish three approaches to information systems corresponding to three levels of concern.

The first level is called the conceptual approach, the second the logical approach and the third corresponds to the concrete realization of the latter.

These three levels can correspond to three types of the project owner who wants to set up a system in order to solve operating problems, the problems, the project owner who has to find a solution to meet the project owner's request, and that of the developer who will create the system.

These levels of concern are translated into action by the main steps of a process aimed at ensuring the success of the system to ensure success the system, steps that are recommended when a study is launched to implement or improve an application using an information system.

The conceptual level specifies the actors involved and the functions performed by the information system as well as The conceptual level specifies the actors involved and the functions performed by the information system as well as its limits of use, i.e.

the functions that it does not perform (What do we want to do?).

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The logical level of the information system specifies how the expected functions are achieved:

what is the

realized: what is the necessary information and which treatments are going to use it in order to realize the objectives (How are we going to do it?).

The design at this level of the system only takes into account

the requested functionalities independently of the technical means used for its realization.

The last question is: With what do we realize the information system? It is intended to intended to specify the tools used and to estimate the developments to be made.

There is a fundamental principle to be applied in all circumstances: the independence of processing and data to ensure the scalability of the system.

Indeed, this principle, which is simple to state but more difficult to achieve guarantees that if it is applied the form of the data does not interact with the developments and vice versa.

This means that if the data changes, the existing processes will continue to work and in the same way, any modification of the processes will be possible with the existing data.

The independence between the two components of a system will not be realized if for example the data a particular structure or specific properties such as a particular order in the list of attributes.

the particular order in the list of attributes.

Information system
Conceptual level
Global data
Example of the budget forecast
investment authorization
Logical level
Description of theoretical data
Example division of the budget into chapters
lists of accepted forecasts
Level of realization
Physical support of the data
Files
Books

The MERISE or UML methods are perfectly adapted to the implementation of an information system and include the three previous levels: conceptual level, logical level, and realization level.

The MERISE method, for example, imposes a study according to these three levels for both the treatments and for the data.

By carrying out this double approach we respect by default the principle of independence since the study on the treatments will be carried out independently of that on of the one on the data.

The method leads to the realization of several models:

The conceptual data model (CDM) specifies the necessary elements,

The logical data model (LDM) translates the conceptual model into concrete terms by indicating the properties of each element.

The conceptual processing model (CPM) indicates the functionalities to be provided and the methods to achieve this.

The logical processing model (LPM) describes the different operations necessary to obtain the previous functionalities.

The implementation of the data and the development of the processes constitute the remaining levels.

The step-by-step approach allows, in particular, to take into account the hardware constraints only at the end.

This guarantees the reuse of the conclusions of the previous stages, which is particularly interesting in order to ensure the This is particularly interesting in order to ensure the maintenance of the system.

A modification of a conclusion of a step will only have an influence on the following steps.

5/11/2021

General: Information Systems/ Introduction

5/11/2021

General: Information Systems/ Introduction

Introduction Geographic Information

The amount of information available to man has never stopped growing for many centuries.

In order to satisfy his ever-growing development needs, the latter has been forced to explore unknown lands or destinations to discover their potential wealth, estimate them, and exploit them. Over time, it has sought and developed technologies and technologies and methods in order to produce more efficient tools, consumer goods or to exploit them.

tools, consumer goods or to travel faster.

Each discovery generated its share of information recorded on various supports allowing one to keep a trace of it to be able to share them with others.

This information concerned in particular the events or the events or remarkable details of the territory.

Their descriptions had to be as accurate as possible in order to faithful as possible in order to allow an audience to perceive the main characteristics without having directly witnessed the main characteristics of the event without having witnessed it directly and to estimate its importance accurately.

An event is described by characteristic details such as its nature and importance, the date on which it took place, and the place where it took place.

The localization was done thanks to place names, references to topographical details, or by positioning on a more or less detailed map.

The sciences and techniques by becoming more and more complex have made impossible the universal knowledge and led to segmentation of knowledge and to a specialization of researchers and technicians, each one having its own needs and its own approaches.

The collection of useful information has required an effort of presentation or synthesis to meet the needs of specialists, especially when a phenomenon concerned several research fields, each requiring
research fields, each requiring thematic information.

The diversity of information has obliged us to resort to methods of description that have been refined according to the needs of each specialist and the technological evolutions.

At the time of the navigators who set out to the discovery of unknown lands, the information was written in the very general logbook by the commander of the fleet who scrupulously noted all the events, whatever their nature.

The following expeditions allowed the writing of specialized books thanks to the presence of scientists on board, botanists or astronomers for example, who related the facts or discoveries concerning their field.

The logbook could then be limited to maritime events.

Finally, over the centuries, the successive discoveries and the progress of science allowed the publication of more and more specialized works on extremely specialized subjects in more general fields.

Recently, the arrival of computers and databases has allowed a dematerialization of knowledge while requiring a rationalization of the information in order to adapt to the constraints linked to computers, the natural language used in the books not being adapted to the latter.

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Geographic Information

Among all the data manipulated by scientists or engineers, those having the property of being localizable, in an absolute or relative way, is called geographical.

They have followed an evolution similar to the purely scientific data, slowed down however by their
very general fields of use, by the complexity of their manipulation and their creation, as well as by the
absence of powerful means.

For a long time, the map has been the federation of this localized information, because it was the only existing medium capable of representing multiple themes containing localized information.

But information needs have

information sources have multiplied and users now demand rapid availability of up-to-date data, as well as rapid dissemination.

Many sciences and technologies are involved in the production, presentation, dissemination, and use of
localized data: they are gathered under the banner of Geographic Information.

Its fields of action include the techniques of data capture or more generally of production, formatting, storage, presentation of data as well as the methods allowing their use, in particular those facilitating the analysis of a territory.

A lot of information circulating today is more or less directly endowed with a geometric component.

Without the techniques of Geographic Information, the geometric information cannot be made available as quickly as the rest of the knowledge, and analyses can be incomplete without taking into account the neighborhood relations between the treated elements.

It is thus called to be more and more present in the information circuits.

The fact of using information with a geometric component makes it possible to take into account
physical or descriptive properties of the elements of the territory, and the interactions between entities as a consequence of their proximity, their overlap, or their relative position.

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General: Information Systems

Often when useful information is dispersed among several users, its access is made difficult, if not impossibly difficult, if not impossible, without a minimal organization and without the help of a tool allowing to search for it: this is the information system.

The difficulty of gathering information generally hinders its use and sometimes its use and sometimes hinders the obtaining of results using elements of information disseminated among several owners.

In addition to the fact that the very knowledge of their existence can be a problem in itself, it is not enough, and the location or the search for information, elements can generate difficulties sometimes insurmountable or too expensive to justify their use.

Intended to gather information and used to information systems have become indispensable tools for any entity managing information.

This information can be financial, technical, or documentary.

These systems gather and manage large amounts of information and allow access to this information by finding the information sought or by indicating at least the place or the place or medium containing it.

The available information is then valorized because its

the organization will allow an advanced consultation, allowing the realization of products with added value (analyses, calculations, references).

They are indeed used to improve the knowledge of an entity like a company, a laboratory, or a library.

For example, they can help in decision-making by providing measurement tools with the necessary information to describe the state of a part or of the whole of the latter (such as a financial or accounting balance sheet).

By allowing to gather information, they provide a working tool that can be shared by all employees who thus have access to all the information and not only to the one they have or the one that they possess or know about.

They offer the possibility of aggregating data in order to calculate global indicators that meet the needs of decision-makers who must have reliable information, synthesizing the elementary operations carried out, in order to estimate the and capacities of the company.

They also allow simulating situations by calculating the influence of the evolution of one or more parameters on the others or on the global balance sheet.

They provide the data and associated processing allowing to carry out syntheses and various analysis.

Data are often managed by means of database management systems (DBMS) which
storage of data of all kinds, then carry out the research, the extraction, and the presentation of
the information necessary for the treatments required elsewhere.

GENERAL: INFORMATION SYSTEMS/EXAMPLE OF A PRODUCTION COMPANY AND GENERAL DESCRIPTION PART 2

5/04/2021

Positioning and reference/ Geodesy

5/04/2021

Positioning and reference/ Geodesy

Geodesy

Geodesy is the science that studies the dimensions and shape of the Earth and the variations in its field of gravity, all as a function of time.

Measuring the size and determining the shape of a small object is relatively simple. For example, a soccer ball is a sphere (shape) whose size (diameter) can be determined with a tape measure. Because of its size, it is easy to measure the figures that make it up.

For the Earth, it is a little more complex. It is necessary to set up a frame of reference to integrate the different types of measurements that can be made. A frame of reference is a tracking system through which it is possible to locate an event in space and time. For our purposes, such a referential is called a terrestrial reference system, also known as a geodetic reference system.

A terrestrial reference system is a set of parameters and conventions for determining the position of a point in three-dimensional space. The position of a point in this system is expressed in Cartesian coordinates (X, Y, Z) or geodetic coordinates . To obtain geodetic coordinates, it is necessary to work with an ellipsoid, i.e. an ellipse that rotates on itself. Why an ellipsoid? Because the Earth is not a perfect sphere, but slightly flattened at the poles. The difference between the diameter at the equator and the poles is about 52 km. Geodetic coordinates are best known in terms of latitude, longitude, and altitude (h) .

Cartesian and three-dimensional geodetic coordinates

The field of gravity

The geoid

The gravity field plays an important role in the shape of the Earth. The Earth is a complex plastic body composed of solid, semi-rigid, and liquid parts. Since these different parts are not made of identical materials, the gravitational field differs from one place to another.

The measurement of gravity makes it possible to define another surface representing the shape of the Earth: the geoid. This surface gives an approximation of the mean sea level. It is made up of hollows and bumps caused by the uneven distribution of masses of various densities.

Moreover, being a plastic body, the shape of the Earth changes continuously. It is subject to different internal and external forces.

Influential forces

For a person, these changes may be perceptible, such as the tide, or imperceptible, such as the land tide (amplitude of about 30 cm) and the drift of lithospheric plates (tectonics). To track the movement of the plates, a four-dimensional reference frame (three axes and time) independent of the earth's surface is required. The International Terrestrial Reference System (ITRS) has this temporal capability. Unlike the ITRS, the NAD83 system is fixed to the North American tectonic plate. The position of the points is invariable in time unless they are located on an unstable part of the plate.

The main tectonic plates and their drifts

The GPS

In the past, the stars allowed navigators to position themselves. Today, GPS satellites have replaced the stars and unlike the stars, satellites are accessible 24 hours a day despite the clouds.

The arrival of the GPS (Global Positioning System) has revolutionized the way of doing things in the field of positioning and navigation. Set up, controlled, and operated by the United States Department of Defense (DoD), the GPS system is based on a constellation of satellites that allow a position to be determined at any time and in any place on Earth. This constellation is made up of at least 24 satellites operating at an altitude of approximately 20,200 km.

GPS satellite

The GPS constellation

Each satellite transmits on two carrier waves different coded messages containing civil and military information, including its position in the WGS84 terrestrial reference system. Civilian information is broadcast on a single carrier wave.

The principle for obtaining a position is very simple. Using the coded message transmitted by a satellite, a GPS receiver determines the time it took for the signal to travel the distance to that satellite, approximately 0.07 seconds. By multiplying the time obtained by the speed of light (300,000 km/s), the receiver can determine this distance. Thus, measurements on four satellites allow the position of the receiver to be determined. The accuracy of this position varies from ten meters to one centimeter and better depending on the type of receiver used.

When calculating its position, the GPS receiver synchronizes its clock with the atomic clocks of the GPS satellites. Once synchronized, the receiver displays the time with a very high degree of accuracy and in turn, becomes a very precise time reference.

Consumer receiver

The vast majority of users of GPS receivers have a positioning need of the order of ten meters. This is the accuracy obtained with a single receiver reading the coded message from a minimum of four satellites.

Receiver for differential positioning

Another level of accuracy is between 0.5 and 5 meters. To obtain it, it is necessary to read the coded message with two GPS receivers simultaneously. This is called differential positioning.

Receiver for carrier wave positioning

Carrier wave positioning is the most accurate, ranging from 30 cm to better than one centimeter. Instead of reading the coded message with two receivers, the receivers measure the wave that carries the coded message. Usually, these are specialized receivers. However, this method is very sensitive to obstructions that can cut off the signal.

Differential positioning and carrier wave positioning requires the processing of data collected by both receivers.

This processing can be done in specialized software once all the data has been collected, commonly called post-processing, or in real-time if there is a communication link between the two receivers.

This link is used to transmit data from one receiver (called the base) to the other. The receiver that receives the data (called the cell phone) has software to process the received data on its own.

The accuracy of the position can vary from a centimeter to about two meters depending on :

- the distance between the two receivers;

- the time it takes to capture the data;

- the type of receiver used in the field;

- the way the data is processed.

The Ministère des Ressources Naturelles has set up permanent GPS reference stations throughout Québec to serve as a base for applications requiring differential positioning or carrier wave positioning. These stations allow positioning by post-processing and the majority of them offer real-time centimetric positioning by cellular telephony.

Why use geodesy and GPS?

Although little known to the general public, geodesy is the basis of everything related to terrestrial positioning.

A reference system resulting from geodesy allows to position oneself and then to position different works in a common reference frame.

Its infrastructure of points (geodetic network) is indispensable not only for the precision and homogeneity of maps but also :

- to navigation (land, sea, or air);

- geophysics;

- Space science;

- Atmospheric sciences;

- Prospecting;

- knowledge of continental drift;

- monitoring of oceanic phenomena;

- everything related to earth sciences.

Thus, for geophysics, geodesy provides :

- information for the study and modeling of the deformation of the Earth's crust over time;

- Gravimetric data to study irregularities in the distribution of crustal density and its variation over time.

For space sciences, geodesy provides :

- the geometry of the gravitational field necessary for the prediction of satellite orbits. This contribution will further increase in view of the current and future exploitation of increasingly efficient space resources.

The advent of geographic information systems has exploded the need for location in a single repository in order to integrate and share data from different sources.

Thanks to the advent of GPS, the notion of positioning has become democratized.

There is a multitude of fields in which this cutting-edge technology is used with or without the help of a geodetic network :

- air transport

- cartography

- surveying

- navigation

- telecommunications

- remote sensing

- regional/recreotourism development

- civil security

- agriculture

- forestry

Pilots use GPS to guide their aircraft.

Geodetic points are used for photogrammetric purposes, thus for map-making and the collection of data from geographic information systems.

GPS and geodetic points are used, among other things, for topographic surveys, subdivisions, and infrastructure construction (bridge, road, dam, etc.). Cities and other service agencies use them to locate their infrastructures such as power lines, fire hydrants, and even streets.

At sea, fishermen and sailors use them as a guide to navigate or to locate places.

GPS receivers are used to synchronize telecommunications networks.

The addition of GPS receivers aboard low altitude satellites allows for more precise measurement of their location and more accurate analysis of their orbit.

Hikers, campers, and hunters use it to avoid getting lost.

It is used to track vehicles in real-time (fire, ambulance, or other 911 services), to locate persons in distress, etc.

Farmers use it to better manage their farms (precise application of seeds and herbicides, etc.).

Foresters use geodetic points and GPS to carry out forest inventories and to locate forest roads.

8/13/2019

satellite images / Remote sensing

8/13/2019

satellite images / Remote sensing

satellite images

Remote sensing

Remote sensing is used for Earth observation. This is a technique that allows you to acquire information on a ground target from a satellite.

Information received by satellites is digitally recorded using electronic sensors.
The information is then recorded as an image and transmitted to receiving stations on the ground. Onboard satellites, the sensor records images in the form of spectral bands.
Each of the spectral bands gives a black and white image, where the shades of grey vary.
By superimposing three spectral bands with color filters, it is possible to obtain a color image or a color compound.
Each colored compound gives different information on land use.

Landsat-TM satellite image at 25 m resolution Sheet 35E

Lake Lanyan - Nord-du-Québec

The resolution of the images

The sensors onboard the satellites each have their spatial characteristics for recording images. In remote sensing, we do not speak of scale as in aerial photography, but of spatial resolution, which gives the accuracy of images.

The resolution of an image is determined by the smallest area that the satellite can detect on the ground. This surface is expressed in the image by pixels, an acronym formed by the words "picture element". A series of pixels make up a satellite image. This is also the case for a photo scanned by a computer.

Thus, the example opposite of a small red fox shows that the more a photo is degraded, the more blurry it becomes until it perceives the pixels.

Thus, when we say that an image has a resolution of 30 meters, it means that each pixel that constitutes the image represents an area of 30 meters by 30 meters on the ground.

So, the higher the resolution of an image, the more accurate the image.

However, the higher the resolution, the smaller the area covered by the image. So, what we gain inaccuracy, we lose in the big picture. The example of a baseball field in images of the La Baie region in the Saguenay region illustrates this phenomenon:

the image taken by a satellite at a resolution of 10 meters makes it possible to observe the location of the land and its environment;
the image taken by an aircraft at a resolution of one meter allows the baseball field to be circumscribed and details to be seen within the field itself.

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Why use satellite images?

Satellite images are very rich in information of all kinds. The information obtained from satellite images not only makes it possible to produce and update maps but also to analyze various aspects of the territory. Satellite images are generally not as accurate as aerial photographs, but they cover large areas and allow for regional analysis.

agriculture
forestry
geology

agriculture

Satellite imagery allows agricultural producers to obtain information on their territory to manage crops more effectively.

This technology allows them to plan operations and anticipate risks that could threaten their production. For example, they can use it to predict the risks associated with insect infestations, bad weather, droughts, etc. In agriculture, satellite images are used, among other things, to:

classify the main types of culture;
assess crop health;
estimate the total production of a crop;
map soil management practices;
monitor compliance with laws and treaties.

forestry

Satellite images are used to obtain information on forest cover types (inventory of large groups and sometimes species), on vegetation density, and the decrease or state of resource regeneration.

They are used to observe the harvests carried out and to monitor the quality, health, and diversity of forests. These tools are very useful for forest resource management and for improving mapping on the subject.

geology

Studies in this area focus on landforms, structures, and the earth's crust to facilitate understanding of the physical processes that modify the earth's crust.

Satellite imagery is an interesting tool in this field since it allows to extract of information on structure, for example, faults and folds. This information is often combined with other data sources to obtain additional measures.

Satellite imagery also allows for planning and logistics, such as planning field campaigns or access roads in a mining area, monitoring projects, and creating base maps on which geological data can be overlaid.

Here is a list of the main applications of satellite images in geology:

mapping of surface deposits;
mining and petroleum exploration;
environmental geology;
mapping and monitoring.

8/09/2019

aerial photography

8/09/2019

aerial photography

AERIAL PHOTOGRAPHY

See in three dimensions

Aerial photography is an image taken vertically using a specialized camera, installed onboard an aircraft equipped for such work.

Aerial photography is always done so that two photographs have the same longitudinal and lateral coverage. These overlaps make it possible to observe the territory in three dimensions, using a specialized device. The optical phenomenon that allows a three-dimensional vision is called stereoscopy.

The photo interpreters use stereoscopes to view the photos in 3 dimensions. These specialized glasses make sure that the right eye looks at the right photo and the left eye looks at the left photo, then our brain reconstructs the image in 3 dimensions!

In order to obtain a three-dimensional view of the territory covered, a part of the ground represented in one photograph must also be present in the next. This is called a collection. As the aircraft moves, the area photographed, which is common in both aerial photographs, provides a view of the territory from two different angles. By looking at this part with a stereoscope, it is possible to get an overview of the relief since it appears in three dimensions.

60% longitudinal overlap for stereoscopic vision;
30% lateral coverage to ensure complete coverage of the territory

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Stereoscopy reproduces the natural process of three-dimensional vision in our eyes. Taking two images at different angles, by an aircraft, allows us to reproduce the vision of our two eyes. It is the distance between the two images and the height of the aircraft that accentuates the three-dimensional effect.

These images from the Megantic and Orford region show a simulation of what can be seen by looking at two three-dimensional aerial photos, without stereoscopes or glasses to see in 3D!

- The images on the left are mosaics of about twenty color aerial photographs at a scale of 1:15,000, which show a large area in one piece.

- The images of the center are called Digital Elevation Models (DEMs) and were produced from the contour lines found on the 1/20,000 scale topographic maps. These MNA present, in images, the relief of these regions.

- On the right, the result of the combination of the MNA and photo mosaics: Mont Mégantic and Mont Orford in perspective and in all their splendor!

Mont Mégantic

Mont Orford

Another way to see aerial photos in 3D and, this time vertically, as you would see them with a stereoscope, is the anaglyph process. This word is taken from the Greek word anaglyphs which means "carved" or "embossed".

In these examples, it is an overlay of two consecutive aerial photographs (the area where there is a longitudinal overlap) of Mount Orford on the left and the Hautes-Gorges-de-la-Rivière-Malbaie on the right. The use of two complementary colors, here red for the left image and cyan (blue-green) for the right image, allows the relief to be reconstructed by looking at the composite image through "3D" glasses equipped with colored filters. Each eye sees only the image that suits it and the brain merges the two images to give the illusion of a single relief image.

Aerial photos of the Hautes-Gorges-de-la-Rivière-Malbaie taken on May 23

Note: Red-cyan anaglyph 3D anaglyph glasses are available in different locations, such as photoshops, or on the Internet. But maybe you had some with your latest DVD? in 3D? You can also make your own glasses using red and cyan acetates, quite simply!

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The different types of aerial photos

Aerial photographs are images of the territory taken on a given date and are used to interpret the forms and details that characterize it. The interpretation of shapes, shades of color or grey and textures makes it possible to distinguish the details present and their nature. For example, it can be interpreted:

hydrography (lakes, rivers, streams, ponds, ponds);
vegetation (woodland, wetland, crops);
inhabited areas;
transport infrastructure (roads, forest roads, trails);
the bonfires and burns.

Generally, 1:5,000 scale shots are reserved for urban areas, while 1:15,000 and 1:40,000 scale shots are generally used in the southern part of Quebec, south of the 52nd parallel of latitude, for topographic and forest mapping purposes.

The raw image, as taken on board the aircraft, can be developed and printed on film or slide paper.

The following are the types of aerial photographs most commonly used by departments and agencies for land and resource management:

Aerial photographs in black and white at scales of 1:15,000 and 1:40,000

Black and white aerial photography is stored on panchromatic emulsion film (black and white). This emulsion makes it possible to print on photo paper a range of about 50 different shades of grey, which represent different objects on the territory.

On 1:15,000 scale aerial photography (left), there are more details, including roads, than on 1:40,000 scale aerial photography (right).

Aerial photographs in color infrared and color at a scale of 1:15,000

- These aerial photographs are stored on negative color or color infrared emulsion film. This type of emulsion makes it possible to reproduce aerial photographs in color infrared and color.

Aerial color infrared photography is mainly used for forest inventory work. This example from the

Saguenay - Lac-Saint-Jean watch that it is easy to delimit and map the forest cuts, in blue.

- Colour photography can be used for many purposes: forestry, agriculture, land use planning, etc.

This aerial photograph of the Estrie region shows the diversity of these uses.

When it is digitized and corrected and has the same geometric location properties as a map, it is called orthophotography.

Orthophotography is an aerial photograph:

- which has been scanned digitally in high resolution;

- which has been geometrically corrected and straightened from the ground to eliminate inaccuracies caused by camera tilt at the time of the shooting and due to image distortion caused by terrain;

- to which the coordinates (georeference) have been added;

- which can, therefore, be used in a computer to superimpose other geographical information, measure distances, etc.

Orthophotograph showing the landslide in Nicolet in 1955. The rectified photograph can be superimposed on a map to show which buildings were washed away by the landslide.

These orthophotographs of the Ha! Ha! in the Saguenay show the extent of the damage before (left, photo of May 27, 1996) and after (right, photo of May 10, 1998) the famous flood that occurred on July 20, 1996. We can even see that the river has changed its course.

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Photos of the future...

More and more, aerial photographs are taken directly in digital mode, with digital airborne cameras. These digital airborne images are taken, in the same way as satellite images, by electronic detectors. Therefore, as with satellite images, their accuracy is given in terms of resolution and not scale. In addition, these cameras simultaneously take panchromatic images (in black and white) and color images that are also called multispectral (in red, green and blue). Panchromatic bands are generally of higher resolution.

The great advantage of using airborne digital cameras is that there is no film, so there is no development operation. In addition, the photo does not need to be scanned to produce a digital image and is easier to store. Finally, these images have great qualities, since they are both in good resolution in black and white and in color.

On the other hand, the great advantage of traditional cameras is their wider field (they cover more territory per shot) and their price is much lower than that of large format digital equivalents.

Why use aerial photographs?

Aerial photography is very rich in information. Among other things, it can be used to identify streams, ponds, trails, and clearings that are not shown on a map. It can also identify bonfires and burns, and determine changes and types of vegetation. However, the undeniable advantage of aerial photography remains the possibility of obtaining a three-dimensional vision of the territory through stereoscopy and thus giving an insight into the relief.

Orthophotography is halfway between aerial photography and topographic mapping. It offers the detail and richness of an aerial photograph, combined with the geometric accuracy of a map. Since it is georeferenced, it can be superimposed with geographic information such as:

hypsometry (representation of the relief);
toponymy (place names: lakes, rivers, road network);
territorial boundaries (administrative boundaries, boundaries of recreational and protected areas).

By their nature, aerial photographs and orthophotographs provide an overview of the territory at a specific time in time. This is why they are used to obtain information about the past or even to plan projects.

Back in the past...

Aerial photography can be used as an archive. Indeed, it allows going back in time by performing the photo-interpretation of a shot taken a few years before.

Here are some examples of the use of old aerial photographs for various fields of activity:

justice
land-use planning
civil security

justice

When the land on a property is in dispute, old aerial photographs are often used to obtain information on the condition or delimitation of the property before the changes that caused the dispute. In such a case, these photographs become very reliable support for establishing evidence.

land-use planning

Old aerial photographs are often used to redevelop the site as they were in the past. The photographs will then be used to prepare the basic elements of the urban development master plans.

civil security

Aerial photographs can be used to assess the extent of damage caused by a natural disaster.

Flooding in the Saguenay
The ice storm

The witness of the evolution...

Aerial photography, when taken in an urban environment, makes it possible to show the stages of urbanization or its spread by the juxtaposition of images captured at different times.

Here are some examples of use for various fields of activity:

land-use planning
forestry

land-use planning

Aerial photography makes it possible to study the evolution of urbanization over time.

forestry

It is used to obtain information on the physiognomy and groupings of forest species (stand types). It also makes it possible to assess forest potential, since it is possible to inventory forest resources and obtain an approximation of the volume of wood. Thus, the evolution of tree species or cutting areas can be more easily monitored to ensure proper management.

A vision of the future...

Aerial photographs can be used to conduct site research analyses or plan large-scale projects.

Here are some examples of how to use it for project planning:

civil engineering
agriculture

civil engineering

Aerial photographs can be used to search for sites (factories, dams, ports, etc.) or to make preliminary network projects (roads, railways, canals, power transmission lines, pipelines, etc.). They can also be used as orthophotographs to take measurements, add layers of information, plan and even make project models.

agriculture

Aerial photographs are used to predict crop yields, estimate crop damage caused by insects, diseases or floods, assess soil water balance, discover areas affected by salinization, etc. They provide good forecasts of agricultural potential.

7/27/2019

Geography / cartography

7/27/2019

Geography / cartography

The geography

Geography is the science of knowing the current, natural and human aspects of the Earth's surface.

The geography allows us to understand the spatial organization of phenomena (physical or human) that manifest themselves in our environment and shape our world.

Geographic information includes all data that can be located on the territory, in the form of points, maps, tables, images, etc. It provides information on:

the territory;
the location and distribution of natural and environmental resources;
infrastructure (roads, buildings, equipment, etc.);
population (socio-economic characteristics, socio-demographic characteristics, etc.);
administrative and legal areas.

Geographic information is collected, for example, from aerial photographs, and then this information can be recorded on a map. But today, it can also be organized, structured and stored in databases. These databases integrate the physical location and description of objects on the Earth's surface. Geographic information can then be used in a geographic information system by a very large number of users.

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The data

The use of geographic data began at the beginning of the colony. The explorers carried out measurements on the territory to:

subdivide them into seigneuries;
manage port and military infrastructure;
locate sea and land routes.

Today, geographic information on the Quebec territory is used by more than a hundred users whose concerns are very different. Land management requires the knowledge of data often linked to the same space for:

reconcile their various activities;
promote consultation;
enable the resolution of complex territorial problems.

Data acquisition is done through field surveys, satellite images, aerial photography, maps or the use of GPS surveys.

Structuring consists of verifying the conformity of the data and establishing the relationship between the different elements.

Storage allows geographic information to be stored in databases. These databases store the geometry of the elements as well as the descriptive data related to these elements.

Processing makes it possible to use the geographical database to study a phenomenon, i.e. to analyze it, model it and establish cause-and-effect relationships with a spatial impact.

Dissemination consists of conveying information in the form of raw data, tailor-made products or processing results. Information can be transmitted on paper, such as a map or image, on a digital medium, such as a CD-ROM or a telecommunications process, or on the increasingly used Web.

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The cartography

The cards

Mapping is the art, technique, and science of map-making. It allows the geographical representation of the natural and artificial elements of a territory, such as a road, a river or a lake, in a system of terrestrial coordinates. A map is always presented at a specific scale, which varies according to the detail or portion of territory to be represented.

A map is the projection of a curved surface such as an ellipsoid or a sphere, or part of it, onto a plane. This is called a cartographic projection. Different types are depending on the size and shape of the territory to be mapped. The most commonly used projections in Quebec are the Transverse Mercator (cylindrical projection) and the Lambert Conformal Conic (conical projection).

The use of geographic data and maps is not new. From the beginning of the colony, explorers carried out measurements on the territory to subdivide it into seigneuries, manage port and military infrastructures or locate maritime and land routes.

There are several types of maps that are grouped into two main groups.

Topographic maps contain information:

planimetric (hydrography, roads, buildings, vegetation, equipment, place names, etc.); and
hypsometric (contour lines and dimensional points).

-Topographic maps are the official cartographic foundation of the Government of Quebec.
This information, also called reference information, comes from government programs and missions. It gives land managers a common spatial reference. It is to this basic geographical reference that the thematic data specific to each department and agency are added.

-Thematic maps provide information on specific themes such as the road map, land use map (example below), geological map, forest map, etc.

The scales

A map is always presented at a specific scale, which varies according to the detail or portion of territory to be represented. For example:

a large scale map shows a small portion of territory with a lot of detail;
a small-scale map shows a large portion of territory with little detail.

Click the plus (+) or minus (-) to change the scale of the map.

Why use the cards?

The cards can be used to meet a multitude of needs in most areas. A map allows a spatial representation of phenomena on the territory where only imagination remains the limit!

The following are examples of the use of maps in digital or printed form, whether by the professional in the performance of his duties or by the citizen in his travels or the practice of activities on the territory:

forestry
agriculture
hunting and fishing
open-air
transport

A map is very useful in the forestry sector for planning activities on cutting areas and thus allowing better management of the area and resources.

The maps are used to plan various agricultural operations, locate cultivated and non-cultivated areas and crop types. A map can greatly improve the management of agricultural land.

Hunting and fishing enthusiasts use the map and compass to plan their itinerary and orient themselves in the forest.

Maps are used, for example, to plan a bicycle route that can be followed on a GPS receiver to ensure safe travel.

The road map is undoubtedly the most widely used by citizens for their car journeys on the territory.

7/18/2019

GIS: Methods of analysis / GIS TRAINING

7/18/2019

GIS: Methods of analysis / GIS TRAINING

CHAPTER4: Methods of analysis in a GIS

Queries and interrogations

Query, exploration, statistics

Metric measurements and calculations

Metric properties of objects: length or perimeter, surface, etc.
Relationships between objects: distance, orientation

Data transformation

Creating new descriptive attributes
Based on arithmetic, logical, geometric rules

Information synthesis

Scale transfers
Geostatistics and interpolation
Changes in spatial location

Optimization techniques

Optimal locations
Shorter paths, operational research

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Classification methods

Descriptive classification (grouping on a descriptive criterion)

Maintain the form of the distribution
Maintain dispersion: maximize the interclass variance
To reveal the irregularities of the series

Discretization methods (examples)

Classes of the same amplitude
Equal enrolment classes (quantiles)
Use of mean and standard deviation (normal distributions)
Arithmetic or geometric progression
Natural Threshold Method

Examples of methods using localization

Selection of objects on a distance or membership criterion: the creation of buffer zones (or buffer, or mask)
Selection of objects based on orientation or direction criteria
Connecting objects on a criterion of distance or belonging: crossings, hierarchy, aggregation, belonging
Classification by proximity: grouping on a geometric or topological criterion (aggregates)
Proximity and neighborhood operations: geostatistics and interpolation

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Changes in the type of geometric object

From point to point objects: point to the mesh by interpolation, point to the zone by influence (Voronoi) or aggregation, point to the line by creating curves of aggregation
From the objects line to line: line to the zone by expansion or aggregation (weighted by an interaction distance), the line to point (calculation of centroids), the line to mesh by interpolation
From the zone objects: zone to point (centroid), zone to the line (skeletonization), zone to mesh (rasterization)
From mesh objects: mesh to the area (vectorization), mesh to mesh (rasterization and resampling methods)

GIS and remote sensing

Geo-referencing and mosaics

Geometric transformations and photogrammetry
Adjustment and adjustment of values

Which object: point or area?

From pixel to geographical object: processing by zone or by pixel?
The use of semi-joining and aggregation operations

Conventional methods in remote sensing

Different types of satellites, different methods: channels are attributes, indices are methods
Directed and non-directed classifications
Vegetation, building, texture, structure, etc. indices Morphology math.

Urban remote sensing

Aerial photography and orthophoto plans

GIS and interpolation: digital field models

DTM by interpolation

From points or lines by interpolation
Many methods to move from the point to the area: nearest neighbors, inverse distance, Splines, kriging, etc. (deterministic methods vs. probabilistic methods).

DTMs and their methods

Slope, orientation, drains, flows, volumes, visibility, watersheds, etc. Hydrology models.

Representation by illumination, representation in perspective

Distance models, influence models, influence areas

GIS and optimization

Networks and graphs

operational research applications: optimal path
distances along with a network, accessibility problems

Cartography

Cartographic language and graphic semiology

The cartographic language

The components of cartographic language
The elementary graphic signs (point, line, task), the cartographic figurative (built from the elementary signs), the graphic layout (punctual, linear, zonal), the visual variables (shape, size, color, value, orientation, texture-structure, grain).

GIS and mapping

Automatic mapping from a query
Choice of a cartographic projection
Association descriptive attribute - graphics attribute (figurative, layout, visual variables)
Automatic label positioning
Filtering and generalizations

Dressing a map

Graphic scale
North Arrow
Title
Corps Map
Legend
etc...

GIS and the Internet

Software: different organizations

Application and data on a single computer at the customer's premises
The client application and data server over the local area network
Data server and application server over the local area network
Data server and Internet application server, query using an Internet browser

Remote interrogation, dedicated applications

-An "application" organization

-A Client/Server organization

-A server managing the database, responding to requests

-On the customer side, several solutions, for dedicated applications:

CGI
Applet or ActiveX
ASP .Net
JSPX
SVG

An unstable evolving technology.

Available data of uncontrolled quality

Data and metadata: an essential requirement
Quality that is often difficult to assess, data to handle with care, unknown contexts
Extraordinary data servers (USGS, NASA, Google...), but whose free availability is not guaranteed in the long term
Multiple questions on data/information/knowledge ownership

GIS: organization

Project definition and feasibility study

Drafting of specifications describing the objectives and needs of the application.

Evaluation of the necessary data and acquisition flows.

Assessment of the system specifications and objectives in relation to existing systems on the market, to assess the feasibility of the operation and the costs involved.

Final evaluation of the various possible choices in terms of benefits and costs.

Logical organization and functional implementation

General implementation and administrative body (human and financial needs, training and user assistance plans, management of future system evolution based on operating results)

Data acquisition body to manage the various information flows (regular or application-specific flows). This body is responsible for evaluating and describing information sources, access procedures, and acquisition procedures.

Data entry and integration body: structuring, homogenization, validation, coding, coding, entry, control, correction, and integration of data according to the techniques required by the information system.

Data analysis and exploitation body ensuring that user requests and application needs are met according to the specifications.