Term

Definition
Global positioning system. Funded and controlled by the US department of defense. Needs 4 satellites for x,y,z. Reciever computes position, velocity and time. 


Term
Milstones. 1973. 1978. 1995. 

Definition
Architecture improved. First satellite launched. System declared operational. 


Term
Milstones. 1973. 1978. 1995. 

Definition
Architecture approved. First satellite launched. System declared operational. 


Term

Definition
6 orbital planes (60^{o} apart) 4 satellites per plane 58 satellites visible from any point on earth. 


Term

Definition
If we know the distance to satellites, then 1 satellite results in a sphere. 2 result in a circle. 3 result in 2 points. 4 results in 1 point. Only 3 satellites are required in principle. The 4th satellite corrects for timing errors and is therefore always needed. 


Term
Recievers have quartz clocks and accuracy of: 

Definition


Term
For a GPS to measure distance: 

Definition
The satellite sends out a known sequence of patterns and any time difference will be autocorrected once it is noticed 


Term
If a reciever and a satellite clock are out of sync by 1/100 s, 

Definition
distance measurement could be out by 3000 km. The 4th satellite corrects this. 


Term

Definition
are controlled twice a day. Minute differences are recorded and sent with the message to the reciever. A good reciever will understand this message and correct its time. 


Term
Radio signals can pass through: But not throgh: 

Definition
Clouds, glass, plastics and foliage of trees. Buildings and mountains. 


Term
Water vapour and the ionosphere: 

Definition
Influence and change the speed of light. No correction is possible for this problem. 


Term
Accuracy can be decreased because: 

Definition
The sum of all errors can decrease accuracy even if each error is relatively small. 


Term

Definition
Dilution of precision. States that when satellites are far apart the DOP is low and there is a good DOP (angles between satellites are larger). When satelites are close together the DOP is high and there is a poor DOP (angles between satellites are smaller). 


Term

Definition
cm accuracy uses reference point on Earth (benchmark) By knowing position of benchmark, combined errors can be corrected. 


Term
GPS and GIS can be used for: 

Definition
Animal tracking Emergency responses Transportation 


Term

Definition
Creation of a digital database is most important and time consuming task on which GIS depends. 


Term
Most common sources for spatial data 

Definition
hard copy maps aerial photographs remotelysensed imagery point data samples from surveys existing digital data files 


Term

Definition
Heads down: digitizing tablet, hard copy map/ Heads up: on screen digitizing, from images (satellite, air photo, scanned) 


Term

Definition
Use a grid of wires embedded in the tablet to generate a magnetic field which is detected by the cursor. accuracies better than 0.1 mm (better than the 0.5 mm accuracy of the operator) 


Term
Headsdown Digitizing operation 

Definition
Map is placed on digitizing table. At least 4 control points are used (coordinates of these points are known. More control points = better map) Follow selected feature with cursor. 


Term

Definition
Digitizing mode in which operator identifies points to be captured by pressing a button. Advantages/disadvantages: operator selects points subjectively. Different operators will select different points. 


Term

Definition
digitizing method in which points are captured at set time intervals (usu. 10/sec) or on movement of the cursor by a fixed amount. Advantages/disadvantages: generates large number of points (redundancy) and is more demanding on the user. 


Term

Definition
If map is removed from digitizing table, reference points must be reentered. If map has stretched or shrunk, newly digitzed points will be slightly off in their location. Errors on the map are entered into the GIS database High level of concentration is needed Discrepancies across map sheet boundaries (edgematching) 


Term

Definition
lines do not connect polygons are not closed potential topology problems 


Term

Definition
Creates a dangle Creates a dangle node After cleaning dangles, there is a useless line but it does no harm to topology. 


Term

Definition
Tolerance that snaps two points together within a certain (set) distance. 


Term
RMS  Tic registration error 

Definition
Root mean square error represents the difference between original control points and new control point locations calculated by the new transformation process 


Term

Definition
1736. Started a new branch of mathematics: Topology GIS topology is a set of rules and behaviours that model how points, lines and polygons share coincident geometry. 


Term
Topology does not change if you ______________________ and it is independent of __________________ 

Definition
transform, stretch, bend coordinate system and scale 


Term
How features share geometry: 

Definition
adjacent polygons have shared edges  street centrelines and census blocks share geometry adjacent soil polygons share edges. no gaps should exist between polygons there should be no overlapping features 


Term

Definition
unconnected chains  without topology strings of unconnected lines no spatial relationship arcs may not join intersections may not have connecting nodes adjacent polygons may overlap or underlap 


Term

Definition
Topological structure of the digital spaghetti GIS vector data are constructed with topology. 


Term
Three elements of topology 

Definition
Adjacency  sharing common boundary Containment  polygon is enclosed and has an area Connectivity  common link. Arcs are connected by nodes. Allows networks and routes. 


Term

Definition
Uses topological modeling for determining shortest paths and alternate routes. 


Term

Definition
defined by vertices and nodes arcs have nodes as endpoints have direction defined by nodes fromnode and tonode 


Term

Definition
Use arc and arc direction to combine polygons Follow arcs in clockwise direction 


Term

Definition
Arcs have direction and therefore each arc records which polygon lies to the left and right side of its direction Outside the study area is called the Universe 


Term
Connectivity and location slide 

Definition


Term

Definition


Term
more connectivity and location 

Definition


Term
more connectivity and location 

Definition


Term
Geoprocessing is any use of location of features to: 

Definition
Combine attributes (join by location) Overlay features (union, intersect, identity) process based on spatial relationships (buffer, clip, dissolve, merge, append, find nearest feature) 


Term

Definition
Interconnected pathways or networks Features that connect or touch 


Term

Definition
Nearness Use of buffer zones 


Term

Definition
Combines the geometries and attributes of 2 features to create a new output 


Term

Definition
used like a cookie cutter to only use data within a certain area 


Term

Definition
Aggregates (joins) features based on similar attributes (border lines from 2 files are erased with this feature to make both files appear as one) 


Term

Definition
Combines input features from multiple sources into a new feature class (makes rivers from two files into one river file) 


Term

Definition
Merges multiple feature classes together to create a single feature class (makes 2 files 1) 


Term

Definition
Boolean OR Includes all classes from the input in the output 


Term

Definition
Boolean AND Features that overlap in the input will be in the output 


Term

Definition
Map extent of input features Inputfeatures that overlap the identity features will beincluded in the output 


Term

Definition
where continuous data are required distances, proximity, cost surfaces elevation models, soils, climate, habitat, vegetation 


Term
Rasters with nominal data 

Definition
have names or a code. eg, land use, soils, county boundary fir juniper pine spruce 


Term
Rasters that have ordinal data 

Definition
can be categorized have names and are ranked eg. land suitabilty, wildlife suitability, risk  very good good moderate poor 


Term
Rasters that have interval data 

Definition
can be ordered and classed eg. rainfall, population density  700709  710719  720729 


Term
Satellite images or digital images such as aerial photographs or scanned maps have a raster format, but lack: 

Definition
internal format for analysis and modeling 


Term
Vector data representation vs Raster data representation 

Definition
VECTOR: models discrete features with precise shapes and boundaries RASTER: models continuous phenomena and images of the earth 


Term

Definition
aerial photography GPS recievers digitized from map manuscripts sketched on top of raster display contours from triangulation CAD drawings 


Term

Definition
photographed from an airplane satellite image converted from triangulation rasterized from vector data scanned blueprints, photographs 


Term

Definition


Term

Definition


Term

Definition
original resolution without generalization graphic output is more aesthetically pleasing (traditional) most data are in vector format accurate geographic location of data is maintained allows use of topology 


Term
Vector data disadvantages 

Definition
location of each vertex must be stored explicitly continuous data are not accurately represented spatial analysis and filtering with polygons is impossible 


Term

Definition
location of each cell is implied by postion in cell matrix no geographic coordinates are stored OTHER THAN the origin point (bottom left corner) data analysis is fast ideally suited for mathematical modelling and quantitative analysis some discrete data are represented equally as well as continuous data integrates the two data types 


Term
Raster data disadvantages 

Definition
cell size determines the resolution at which data are represented difficult to represent linear features network of linkages are difficult to establish raster maps reflect only one attribute vector  to  raster conversion is often required. Problems occur with generalization of gridcell size 


Term

Definition
Perform a calculation on single cell at a time. Neighbouring cells do not influence result 


Term

Definition
Perform a calculation on a single cell and its neighbouring cells. Neighbourhoods can return mean, standard deviation, sum or range of values within immediate or extended neighbourhoods 


Term

Definition
Perform a calculation on a zone, which is a set of cells with a common value. Cells that form a zone can be discontinuous. Can be statistical or geometric. Area, centroid, perimetre, ranges, sum calculations 


Term

Definition
Perform a computation on a raster as a whole. eg. Euclidean distances, weighted cost distances, watershed diliniation. 


Term
For a perfect overlay of raster data 

Definition
Spatial analyst options must be set 


Term

Definition
Identifies maximum rate of change in value from each cell to its neighbours can be percent slope or degree slope first derivative of the surface curvature uses 3x3 neighbourhood window 


Term

Definition
Percent of slope = rise/run *100 Percent slope *100 = tan (degree slope) 


Term

Definition
Slope direction Identifies the down slope direction or maximum rate of change in value of each cell to its neighbours zero slope aspect assigned value of 1 


Term

Definition
Assign new values to old cell values Make a wide range of values into few meaningfull classes 


Term
Theissen polygons (Voronoi polygons) 

Definition
polygons around points. Any location in that polygon is closer to the point the polygon surrounds than any other polygon centroid 


Term

Definition
Specifies that any circle around 3 nodes in a triangle will not include any other nodes Triangles are made and then perpendicular lines are constructed across the centre of the line connecting two points. then polygons are built. 


Term

Definition
To calculate density from point estimates of a population Output density will be occurances of measured quantity per specified unit of area SIMPLE or KERNAL 


Term

Definition
density for each cell is found by summing the value found in population field for eachpoint found in the search radius and dividing by the area of the circle in area units 


Term

Definition
calculated same as simple but value found in population field is distributed out from each point. Smoother looking output 


Term
Raster calculator is used to 

Definition
enter aglebra expression create new themes (grids) perform complex analysis 


Term
How to make raster calculator results permanent 

Definition
1. By supplying a name for the output function in dialog box [output1] = [input]/1000 > creates temporary file output2 = [input]/1000 > creates permanent file 2. By creating a temporary result and then making it permanent. (right click in TOC  Data  Make permanent) 3. By saving the map document, which makes all temporary files permanent in the working directory, using default output name 


Term

Definition
output = con ([waterdist] > 1000, 1, 0) con  condition (IF) con (condition, true, false) If the value of waterdist is >1000, then the output gets a value of 1, otherwise it gets a value of 0. 


Term
Map algebra operators: Boolean and Relational 

Definition
Boolean: the integer output grid will contain values of 1 (TRUE) or 0 (FALSE) Relational: compare the two numbers. If the result is true, 1 is returned, if it is false,0 is returned. 


Term
What would a wedge be used for when using focal functional neighbourhoods? 

Definition
Analyzing wind patterns. Useful to predict fire patterns. How pesticides from one crop will affect neighbouring crops. 


Term
Spatial interpolation is: 

Definition
A continuous grid from point data Estimation of z values of a surface at an unsampled point based on z values of the surrounding points Value for every cell in the grid is calculated 


Term
4 major methods of interpolation 

Definition
Trend: (polynomial) local, global Inverse distance weighting (IDW) Spline Kriging 


Term
Global polynomial interpolation 

Definition
Uses all points. Local neighbours may over or underestimate May not capture overall sloping plane (trend) Minimize error of prediction To make a bend, use a second order polynomial, for 2 or 3 bends, use third and fourth order polynomials 


Term
Local polynomial Interpolation 

Definition
fit many smaller overlapping planes and use centre of each plane as prediction for each location. More accurate than global polynomial interpolation 


Term
Inverse Distance Weighting 

Definition
weight of a value decreases as distance increases from a prediction location Can be accurate IF elevation samples are relatively evenly distributed and surface characteristics do not change across the landscape 


Term

Definition
Nearest neighbours  integer value defining minimum number of points to be used for interpolation Fixed Radius  distance in map units specifying that all input sample points within the specified radius will be used to perform interpolation Power  defining higher powers puts more emphasis onto nearest points. Nearby data will have most influence and surface will have more detail (will be less smooth) 


Term
Controls of interpolation 

Definition
limiting search radius limiting maximum number 


Term
Barriers of interpolation 

Definition
Barriers  limit selected set of input sample points used to interpolate output z values to only those samples on the same side of the barrier as the current processing cell linear discontinuities Can be used in IDW and Kriging 


Term

Definition
Surface that captures global trends and local variations Bend and stretch surface to pass through all points It is a mathematical function that bends the surface like a rubber sheet to make it pass through sampling points Minimizes total curvature Gently varying surface is calculated Good for surfaces without abrubt changes in elevation or terrain models 


Term

Definition
REGULARIZED  yields a smooth surface and smooth first derivatives (yields smoother surface) TENSION  tunes stiffness of interpolant according to character of modelled phenomenon WEIGHT  between 0 and 0.5. Higher values will yield coarser surfaces when using tension NUMBER OF POINTS  smoother surface with more points 


Term

Definition


Term
When to use spline and when to use IDW 

Definition
IDW is used: when assuming variable being mapped decreases in influence with distance eg. consumer purchase power for retail site analysis SPLINE is used: when variable is a smooth conitinuous surface. NOT GOOD in areas with large variability over small distances. eg. water table, terrain, pollution concentration 


Term

Definition


Term

Definition
Postion, time and velocity 

