ENVSOCTY 3GI3 QUESTIONS & ANSWERS
A Raster Consists of a...? - Answer -matrix of equal sized cells
Organized into rows + columns
1 value for each cell
Why store as a raster vs vector? - Answer -1. Better and faster computation (no
topology)
2. Easier to integrate for remote sensed data
Which datatype is discontinuous, precise in location of data, and uses traditional
cartography? - Answer -Vector data
Which data type does not use topology, no data volume, and has better computation? -
Answer -Raster Data
What is a pixel? - Answer -- basic building block
- area of same width and height
- values have a single output value
- each cell has a bit depth
- values applied to entire pixel, reps either cell centre or entire cell
1 bit depth range of values? - Answer -0 to 1
2 bit depth range of values? - Answer -0 to 3
4 bit depth range of values? - Answer -0 to 15
Unsigned 8 range of values? - Answer -0 to 255
Signed 8 range of values - Answer --128 to 127
Unsigned 16 range of values - Answer -0 to 65535
Signed 16 range of values - Answer --32768 to 32767
Unsigned 32 range of values? - Answer -0 to 4294967295
Signed 32 range of values? - Answer --2147483648 to 2147483647
Floating point 32 range of values? - Answer --3.4028243466-e38 to 3.402823466-e38
Unsigned 64 range of values? - Answer -0 to 18446744073709551616
What types of values can a cell have? - Answer -positive
, Negative
Integer
Floating point
Nodata
What is important about nodata values? - Answer -1. Do not equal zero
2. Represent areas of inadequate information
3. Represent areas user doesn't want to display
What three ways can you treat nodata? - Answer -1. Returned for the location input
+output
2. 'Nodata' ignored and output = any available values
3. Value is estimated
What is Resolution? - Answer -- size of a grid cell
- not necessarily representative of the spatial variability on the ground
What tool changes the resolution size?
When should you use this tool? - Answer -Resample tool
When combining rasters
Smaller resolution vs smaller scale? - Answer -higher resolution = smaller cell size =
greater detail
Smaller scale = less detail shown in display
Small scale (1 : 50 000)
Large scale (1 : 2 500)
What data comes in multidimensional raster format? - Answer -- remote Sensing
- oceanography
- climate
What is multidimensional raster data? - Answer -multiple varibales in a file
Common formats include:
- netcdf
-GRIB
-HDF
What is discrete raster? - Answer -- independent #'s
- known + definable boundaries
- cell values = integers
- nominal / ordinal
Characteristics of Discrete Raster Data? - Answer -- all have value attribute tables
- default VAT = Value + Count
- can add fields
- zones and regions
A Raster Consists of a...? - Answer -matrix of equal sized cells
Organized into rows + columns
1 value for each cell
Why store as a raster vs vector? - Answer -1. Better and faster computation (no
topology)
2. Easier to integrate for remote sensed data
Which datatype is discontinuous, precise in location of data, and uses traditional
cartography? - Answer -Vector data
Which data type does not use topology, no data volume, and has better computation? -
Answer -Raster Data
What is a pixel? - Answer -- basic building block
- area of same width and height
- values have a single output value
- each cell has a bit depth
- values applied to entire pixel, reps either cell centre or entire cell
1 bit depth range of values? - Answer -0 to 1
2 bit depth range of values? - Answer -0 to 3
4 bit depth range of values? - Answer -0 to 15
Unsigned 8 range of values? - Answer -0 to 255
Signed 8 range of values - Answer --128 to 127
Unsigned 16 range of values - Answer -0 to 65535
Signed 16 range of values - Answer --32768 to 32767
Unsigned 32 range of values? - Answer -0 to 4294967295
Signed 32 range of values? - Answer --2147483648 to 2147483647
Floating point 32 range of values? - Answer --3.4028243466-e38 to 3.402823466-e38
Unsigned 64 range of values? - Answer -0 to 18446744073709551616
What types of values can a cell have? - Answer -positive
, Negative
Integer
Floating point
Nodata
What is important about nodata values? - Answer -1. Do not equal zero
2. Represent areas of inadequate information
3. Represent areas user doesn't want to display
What three ways can you treat nodata? - Answer -1. Returned for the location input
+output
2. 'Nodata' ignored and output = any available values
3. Value is estimated
What is Resolution? - Answer -- size of a grid cell
- not necessarily representative of the spatial variability on the ground
What tool changes the resolution size?
When should you use this tool? - Answer -Resample tool
When combining rasters
Smaller resolution vs smaller scale? - Answer -higher resolution = smaller cell size =
greater detail
Smaller scale = less detail shown in display
Small scale (1 : 50 000)
Large scale (1 : 2 500)
What data comes in multidimensional raster format? - Answer -- remote Sensing
- oceanography
- climate
What is multidimensional raster data? - Answer -multiple varibales in a file
Common formats include:
- netcdf
-GRIB
-HDF
What is discrete raster? - Answer -- independent #'s
- known + definable boundaries
- cell values = integers
- nominal / ordinal
Characteristics of Discrete Raster Data? - Answer -- all have value attribute tables
- default VAT = Value + Count
- can add fields
- zones and regions
