GIS (MIdterm Study)

Geography
What are the 6 main things that GIS does with data?
1. Collect Data
2. Store Data
3. Maintain (Edit) Data
4. Analyze Data
5. Output Data
6. Distribute Data
What company created GIS?
ESRI
What are some other GIS Programs? there are 5 of them
1. Geomedia
2. IDRISI
3. Mapinfo
4. Autocad Map
5. GRASS
What is the question you have to ask yourself when using GIS?
“who are your users?”
What do coordinate systems consist of?
-Latitude
-Longitude
-Spherical Coordinates
What does DD stand for?
Decimal Degrees
What does DMS stand for?
Degrees Minutes Seconds
what is the equation for getting DMS (Degrees Minutes Seconds) to DD (Decimal Degrees)?
divide the amount of minutes or seconds you have by 60.

Ex. lets say you are given:
DMS 74 45′ 13″ W, you would then divide 45 by 60 and get .75, or 75 minutes or seconds. which mean that:

DD: 74, 75 W

what is nominal data?
non-numeric, non ranked (Ex. Name)
What is Ordinal Data?
Ranked, No magnitude (ex. 1st, 2nd, 3rd)
What is Interval Data?
Magnitude of difference among your entities, can have an arbitrary 0.
What is Ratio Data?
When you have an absolute 0, when zeo means nothing (for example, where there is no population)
What is Vector Data?
Network of points, lines and polygons. this includes:
-Point
-Nodes
-Lines (which are 1-D)
-Polygons (which are 2-D)
-Cube (3-D)
What is Raster Data?
a grid of uniform sq. cells,each of which has a value.

Ex. Photography, Land cover maps, continuous data.

What is Discrete Data?
entities are separated by boundaries or space
What are some examples of Continuous Data?
-Temperature
-Elevation
-Rainfall
What is Topology?
Study of geometric properties that do not change when forms are bent or stretched.

This Includes:
-Intersection between lines
-Adjacency: polygons are adjacent to each other and when points are within polygons
-Containment

What is a .mxd file?
its a MAP FILE only works when it has (.mdb, .gdb, .shp)
What are .mdb and bdb files?
these are GEODATABASES which include vector and raster.
what are .shp?
these are SHAPE files
what are .shx
these are INDEX files
what are .dbf?
these are DATABASE files (found in the spread sheet)
What is geodesy?
measuring shape of the earth ellipsoid, also refereed to as an oblate spheroid
What are map projections?
representations of the 3-dimensional Earth on a 2- dimensional surface.
which 2 types of projections are considered to be “OK”
CONFORMAL AND EQUIVALENT
What is an Conformal Projection?
The Mercator Projection is a conformal projection with correct shapes for landmasses but great exaggeration of size near the poles.
What is NAD27?
-North American Datum 1927

-Based on the Clarke 1866

-Based on one station in Kansas

What are some other GIS Programs?
-GeoMedia- Intergraph, Remote Sensing

-IDRISI- Clark University, inexpensive, runs on old computers

-Mapinfo- (Troy, NY)- Minor player

-AutoCAD Map- Add-on to AutoCAD

-GRASS- Army Origin

What are some examples of attributes?
Name, size, physical attributes, collected rainfall
Cartographic Spaghetti
lines that do not have topology
Cylindrical Projection
•good for world maps
Conic Projection
good for mid lat regions
Planar/Azimuthal Projection
good for polar!
Gnomonic
light in center of globe
Strereographic
light at far side of globe
Orthographic
light infinitely distant
Datum
Ellipsoid, known points benchmarks
what did Eratosthenes discover?
• Knew that the sun was overhead in Syene cause it went directly down a well

• He then traveled to Alexandria and noticed that there was a slight shadow and was different from syene

• He was able to dertermine the circumference of the earth of 40705 km which is very accurate but not exact.

What is NAD83
-North American Datum 1983

-Has multiple benchmarks

What is UTM?
-Universal Transverse Mercator

-Has 60, 6 degree zones

-Never Negative, the center of the zone 500,000m east of the false origin.

-For the southern hemisphere works by working your way down. Starts with 10 million at the center line and as you go down and will go to approx 3 million.

-Error is usually 1 to 10,000 off.

What is the State Zone Plane?
-Coordinate system based on a standard line running through a small zone.

-False origin: S and W.

-In feet, opposed to to meters.

-WE are in New York East.

What direction are trending zones that are involved in Lambert Conformal?
East-West
What direction does trending zones go in TRANSVERSE MERCATOR
North-South

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