1. Getting the Map into the Computer
CENTENNIAL COLLEGE SCHOOL OF ENGINEERING & APPLIED SCIENCE VS 361 Introduction to GIS
DATA CAPTURE/COLLECTION METHODS
COURSE NOTES
Getting the Map into the Computer

2. Data Collection Can be most expensive GIS activity
Two broad capture methods
Primary (direct measurement)
Secondary (indirect derivation)

3. Data Collection Techniques
Field/Raster
Object/Vector
Primary
Digital remote sensing images
GPS measurements including VGI
Digital aerial photographs
Survey measurements
Secondary
Scanned maps
Topographic surveys
DEMs from maps
Topographic data sets from atlases

4. Stages in Data Collection Projects
Planning
Preparation
Evaluation
Editing / Improvement
Collection / Transfer

5. Primary Data Capture Capture specifically for GIS use.
1. Raster – remote sensing
e.g., SPOT and IKONOS satellites and aerial photography, ,echosounding at sea,
Passive and active sensors
Remote sensing is the science and art of acquiring information about the earth’s surface without actually being in contact with it. This is done by sensing and recording reflected or emitted energy and processing, analyzing, and applying that information.”

6. REMOTE SENSING PROCESS
Source of Illumination (A) - provides electromagnetic energy to the target of interest.
Atmosphere (B) - media by which energy travels through from and to target.
Interaction with the Target (C) - after passing through the atmosphere the energy interacts with the target depending on properties of both the target and the energy.
Recording of Energy by the Sensor (D) - after the energy has been scattered by or emitted from the target a sensor collects and records the received energy.
Transmission, Reception, & Processing (E) - the energy recorded by the sensor has to be transmitted to a receiving and processing station where the data are processd into an image (hardcopy and/or digital).
Interpretation & Analysis (F) - the processed image is interpreted, visually and/or digitally to extract information about the target.
Application (G) - in the form of a map, GIS, and decision.

7. PASSIVE SYSTEMS REMOTE SENSING
Passive sensors can only be used to detect energy when the naturally occurring energy is available. For all reflected energy, this can only take place during the time when the sun is illuminating the Earth. There is no reflected energy available from the sun at night.
Energy that is naturally emitted (such as thermal infrared) can be detected day or night, as long as the amount of energy is large enough to be recorded.

8. ACTIVE SYSTEMS REMOTE SENSING
Active sensors, on the other hand, provide their own energy source for illumination. The sensor emits radiation which is directed toward the target to be investigated. The radiation reflected from that target is detected and measured by the sensor. Advantages for active sensors include the ability to obtain measurements anytime, regardless of the time of day or season. Active sensors can be used for examining wavelengths that are not sufficiently provided by the sun, such as microwaves, or to better control the way a target is illuminated. However, active systems require the generation of a fairly large amount of energy to adequately illuminate targets. Some examples of active sensors are a laser fluorosensor and a synthetic aperture radar (SAR).

9. REMOTE SENSING SENSORS:
Aerial Camera
-Black and white aerial photography
-Colour aerial photography
-Colour infrared photography
Satellite
LIDAR and others...
AERIAL PHOTOGRAPHY
Aerial cameras are the simplest and oldest remote sensing sensor.
Vertical photography provides ‘snap shot’ of the ground from an airplane.
Cameras are designed for rapid sequence of photographs while limiting geometric distortions.
Large format (9”x9”).

10. AERIAL PHOTOGRAPHY...
Electromagnetic waves (light) are radiated through space. When the energy (light) encounters an object, one of three things occur:
reflection by; or
absorption by; or
transmitted through.
Airplane will fly a pre-determined route along flight lines to capture the study at the nominal scale.
50-60% forward overlap.
15-30% side overlap.
The overlap ensures complete coverage and also facilitates three dimensional (stereoscopic) viewing.

11. AIRPHOTO INTERPRETATION……..
Analysis of remote sensing imagery involves the identification of various targets in an image, and those targets may be environmental or artificial features which consist of points, lines, or areas. Targets may be defined in terms of the way they reflect or emit radiation. This radiation is measured and recorded by a sensor, and ultimately is depicted as an image product such as an air photo or a satellite image.
ELEMENTS OF AIRPHOTO INTERPRETATION...
Recognizing targets is the key to interpretation and data collection. Observing the differences between targets and their backgrounds involves comparing different targets based on any, or all, of the visual elements of tone, shape, size, pattern, texture, shadow, and association. Visual interpretation using these elements is often a part of our daily lives, whether we are conscious of it or not. Examining satellite images on the weather report, or following high speed chases by views from a helicopter are all familiar examples of visual image interpretation. Identifying targets in remotely sensed images based on these visual elements allows us to further interpret and analyze.

12. AERIAL PHOTOGRAPHY...
Use of elements…
Shadow
Shape
Pattern

13. SATELLITE IMAGERY…….
A network of satellites put into orbit around the earth to collect environmental data about the earth’s surface. Serve a military purpose and an emerging civilian purpose.
ORBITS SATELLITE IMAGERY...
The orbit is the path of the satellite path around the earth.
Satellite orbits are designed to make the best use of the sensors carried by the satellite varying in height, orientation, rotation relative to the earth
Geostationary satellites have orbits that
enable the satellites to observe and collect
data continuously over the same
geographic area. Weather and
communication satellites are
two examples of Geostationary satellites.

14. LANDSAT SATELLITE IMAGERY...
Launched by NASA in 1972 as the first satellite specifically to monitor the earth’s surface.
The program was commercialised in 1985.
Satellite carries mult-sensors with different spectral bands:
Return Beam Vidicon (RBV)
Multispectral Scanner (MSS)
Thematic Mapper (TM)
Near-polar, synchronous orbits.
Revisit period is every days.
Long life span together with above has generated huge archive of images.
Swath width of 185 m.
LANDSAT SATELLITE IMAGERY...
Launched by CNES of France in 1986.
The program was commercialised in 1985.
Each satellite carries twin High Resolution Visible (HRV) imaging systems that can be operated simultaneously and independently.
Each HRV has two modes:
Panchromatic (PLA) mode
Multispectral (MLA) mode
Near-polar, synchronous orbits.
Revisit period is every 26 days.
Resolutions of 10 & 20m.
Swath width of 60 km.
Has oblique viewing capability that can be viewed stereoscopically.
SPOT SATELLITE IMAGERY...

15. ENVIRONMENTAL & FORESTRY
Primary Data Capture - Vector
GROUND SURVEYING
MINING
ENVIRONMENTAL & FORESTRY
AGRICULTURE
CONSTRUCTION
ASSET MANAGEMENT
MILITARY

16. Pen/Portable PC and GPS
Surveying………..
Locations of objects determines by angle and distance measurements from known locations
Uses expensive field equipment and crews
Most accurate method for large scale, small areas
Examples……
Total Station
Pen/Portable PC and GPS

17. GPS (Global Positioning System)
Collection of satellites used to fix locations on Earth’s surface
Differential GPS used to improve accuracy
GPS “Handhelds”
text
geographic coordinates
photos
video
audio

18. GPS….. Navigation system created by U.S government (NAVSTAR)
Made available for civilian use in 1980
24 Satellites, work in any weather conditions, anywhere in the world 24 hours a
day, and is free!!!!!!!!!
How does it work?
Satellite circle the earth twice daily in a very precise orbit and transmit
Stream of radio signals travelling at the speed EMR (Electro Magnetic Radiation).
GPS receivers pick up this information and…Using trigonometry and triangulation…,
and the speed of EMR as a constant, they calculate the user’s exact location.
We are 11,000 mile from the satellite and our location is somewhere on an imaginary
sphere with radius of 11,000 miles, and the satellite at the center.
We are 12,000 miles from
another satellite. Our location is somewhere at
the intersection of the two sphere.
Adding third as in the GPS
system locates it at one of
two discrete points where the three
Sphere intersect. Correct one is
easily chosen to get the precise location

19. Secondary Geographic Data Capture
Data collected for other purposes can be converted for use in GIS.
1. Raster conversion
Scanning of maps, aerial photographs, documents, etc
Important scanning parameters are spatial and spectral (bit depth) resolution

20. Raster to vector conversion
Scanner
Raster to vector conversion
Digitizer
2. Collection of vector objects from maps, photographs, plans, etc.
1.Digitizing
2. Manual (table)
3. Heads-up and vectorization
4. Photogrammetry – the science and technology of making measurements from photographs, etc.

21. Other Resources… Often geographic data available in text form for free
- Delimited and requires importing
- Conversion
- Add Even theme
Data clearing houses and Data warehouses
Internet

22. ADVANTAGES/DISADVANTAGES MAP DIGITISING...