Topic 05

Question 1

what are geometric transformations

Answer 1

correcting nonsystematic issues

often problems with imagery

one coordinate system to another

raster/vector

Question 2

systemic distortions

Answer 2

predictable errors due to nature of data capture (eg satelitte sensor)

usually easily corrected

Question 3

random distortions

Answer 3

distoritaions that are due to unforseen changes in the sensors geometry

corrected by using ground control points(GCPS) and regression techniques

Question 4

map transformations

Answer 4

transforming digilitzed features or imagery into a particular spatial reference system

Question 5

control points

Answer 5

estbalished known points

Question 6

georeferencing

Answer 6

analyzing individual locations to locate features

Question 7

transformation equation

Answer 7

a mathematical equation that is used to match control points to corresponding locations in a projected oordiante system

Question 8

dufferent levels of mathematical equations

Answer 8

equiarea
similarily
affine
projective

cannot be too exact with control points

Question 9

affine transformation

Answer 9

allow for rotation, translation, skew, and differential scaling while preserving line parallelism

Question 10

changing the resolution (cell size)

Answer 10

decrease amount of oricess in your storage

to make another raster have the same cell values so they can be compared

Question 11

resampling (changing raster cells)

Answer 11

smaller pixel to larger pixel (losing value/information)

cannot go from a larger pixel to a smaller pixel

Question 12

georeferencing raster images

Answer 12

transforming raster involves moving from immage space to coordinate space

Question 13

raster registration

Answer 13

alignment of two rasters

Question 14

georeferencing definition

Answer 14

attaching geographic coordinates to each point in a raster

Question 15

rectification

Answer 15

removing distortions caused by dara capture process

GCPs to known map locations

Question 16

orthorectification

Answer 16

removal of distortions caused by terrain relief

Question 17

rectification steps

Answer 17

1. spatial interpolation (rubber sheeting)
2. Digital number interpolation (resampling)

Question 18

raster resampling

Answer 18

issue with raster in re scaling

cubic convolution
(transitions look better but destroy statistic structure)

transformation and resampling data always involves losing some data quality

Question 19

raster resampling techniuqes (4)

Answer 19

basic types (in order of increasing computation)

nearest neighbour
majority rule
bilinear interpolation
cubic convolution

Question 20

can you chain transformations together

Answer 20

no always use the original

Question 21

nearest neighbour

Answer 21

uses the pixel value from the nearest neighbor
maintains data integrity of the image

Question 22

bilinear interpolation

Answer 22

distance-weighted average of 4 neasrest neighbours

alters the original pixel values

Question 23

cubic convolution

Answer 23

uses teh 16 nearrest neighbours

longer processing times

smoother images

Question 24

root mean square error (RMSE)

Answer 24

with interval/ratio data, accuracy is often described with a root mean square error

standard deviation
deviation between the input and the output

Question 25

positinal error distributions

Answer 25

positional error can be measured aas the difference between measured positive of (x,y) and the true position of (x,y)