Lecture 7 Intro to GIS
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What three compinents are GIS used for?
 spacesatellites
 controlground
 userreceiver (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
Multipath Error

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 groundbased 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 (X_{2}X_{1})^{2} + (Y_{2 }Y_{1})^{2}

How do you calculate physical distance?
you accumulate each straight segment

WHat are some errors to measuring physical distance?
 Slope Errorsmountain
 Network Distance physical distance is less than highway distance
 Centroid Representationwhere 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
travel times

A webpage containing special scripts that dynamically add a map to the page
GIS Mashup

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?
r_{obs }/ r_{exp}

WHat is spatial arrangement?
the way things are placed geographically