Lecture 7 Intro to GIS
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What three compinents are GIS used for?
- user-receiver (ex. GPS on phone)
What does the space segment of GIS consist of?
- a constellation of 24 satellites (21 +3 operating spares)
- medium oribit of 12,552 miles
What are the components of the control segment of GIS?
- they track the location and health of each satellite
- health refers to the errors and clock time on each satellites
- there are 11 stations that can be seen by at least 2 satellites
Explain the user segment of GIS.
- The GPS receivers that are tuned to the radio frequencies from the satellites
- Accuracy for regular GPS is 3 meters
- Selective Availability is the intentional degredation of GPS signals
Explain how GPS works.
- There are at least 3 satellites above you
- A GPS receiver and satellite clocks are precisely and continually synchronized , but there can be errors if your GPS receiver's clock is 0.1 second fast
What are the satellite inaccuracies for GPS?
- orbital bias
- satellite dock bias
What are signal inaccuracies of GPS?
- Troposhperic effects
- Ionospheric bias
This occurs when the GPS signal bounces before it reaches the antenna on the GPS receiver
What are the characteristics of Differential GPS?
- requires 2 receivers (mobile and base station
- corrects its GPS positions using the base station info
- Errors can be within one meter
Explain the characteristics of Wide Area Augmentation System (WAAS).
- THey measure small variations in GPS satellies' signals
- For commercial aviation
- use ground-based wide area and reference stations & geostationary WAAS satellites
How are Triangulated Irregular Networks different from DEM models?
- base on triangle grid (not pixel grid)
- different sized triangles (not equal)
WHat is a centroid?
THe balance point or center of gravity of an AREA
WHat are the two sets needed for geocoding?
- Address Table
- Reference DAtabase
What is the formula for the distance theorem?
D= the square root of (X2-X1)2 + (Y2 -Y1)2
How do you calculate physical distance?
you accumulate each straight segment
WHat are some errors to measuring physical distance?
- Slope Errors-mountain
- Network Distance- physical distance is less than highway distance
- Centroid Representation-where exactly are you measuring to?
- Hard Copy
- Seasonal Variation
What are Isochrones?
Lines of equal time distance
What are two methods of measuring area in GIS?
- Grid Cell Counting Method
- Strip Method
How do you measure the shape index?
- divide the intersection by the unit
- if the distance is close to zero, then they are very close to each other
What is the most common function distance
A webpage containing special scripts that dynamically add a map to the page
What does HTML stand for?
Hyper Tect Markup Language
What is the spatial regression formula?
Price= weight matrices (W)*price+Sq.Ft+age+Median Income+Dist_Marta+error
WHat are some basic rules to HTML?
- characters that denote am html tag (<and>) are referred to as angle brackets
- Tags usually come in pairs
- lowercase is recommended
WHat is the nearest neighbor analysis?
An index to evaluate the clustering of point features
What is the formula for the nearest neighbor statistic?
robs / rexp
WHat is spatial arrangement?
the way things are placed geographically
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