Environmental GIS Exam 1 with
Complete Solutions
(True/False) The size of an ArcMap map document will increase significantly as new
data are added because ArcMap stores a copy of each GIS dataset within the map
document. - ANSWER-FALSE
What are two major differences between shapefiles and geodatabases? - ANSWER-
Shapefiles - single layer per datset, no topology, vector, geometry NOT automatically
calculated
Geodatabase - multiple layers per datset, topoplogy, vector and raster, geometry
automatically calculated
What are two major differences between file geodatabases and personal
geodatabases? - ANSWER-Personal - tied to Microsoft; size-limited (2 Gb)
File - not tied to Microsoft; large sizes possible (up to 1 Tb)
How does an enterprise geodatabase differ from a file geodatabase? - ANSWER-
Enterprise geodatabase - DBMS (database management system) linked; multi-user
editing
File - not access-based; proprietary
Define topology - ANSWER-Shape-invariant (unchanging) spatial properties of lines or
polygons such as adjacency, contiguity, and connectedness, often recorded in a set of
related tables.
Raster compression methods may actually result in larger storage than uncompressed
data. Describe how that might happen. - ANSWER-Run-length encoding creates a table
with the value, length of that value, and row of the run. This is very effective for
compressing data with long strings of identical values however in data sets with
constantly varying values run-length encoding can actually create a larger dataset.
Dataset compression is not important today because of cheap storage devices (T/F) -
ANSWER-FALSE
Name two raster data compression methods discussed in class. - ANSWER-Run-length
and value point encoding
What raster dataset property strongly determines the relative effectiveness (percent
reduction in dataset size after compression) of a data compression technique? -
ANSWER-The number of contiguous cells with the same value
, When performing vector to raster conversion of a polygon layer, how does ArcMap
(using the default conversion method) determine a cell value when the cell is comprised
of parts of multiple different polygons? - ANSWER-ArcMap will use the polygon that
crosses the cell center
Why is UTM not a good coordinate system to use for land areas with a predominant
east-west extent? - ANSWER-UTM zones standard parallels run N-S making it good for
mapping areas with the same extent; also if an area has an E-W extent it may cross a
UTM boundary and since each UTM boundary has its own coordinate system, making
analysis difficult
In ArcGIS, as long as you have the map projection correctly specified, you don't need to
worry about datum corrections (True/False) - ANSWER-FALSE
State Plane is a standardized coordinate system that is used by all states so that data
can be shared easily across state boundaries (True/False) - ANSWER-FALSE
When performing vector to raster conversion of a polygon layer in ArcGIS, explain what
options you have to help you control what value will be assigned to a cell that has
multiple features within it. - ANSWER-1) Cell center - feature that crosses cell center will
be assigned cell ID
2) Maximum area - single feature with greatest area will be assigned cell ID
3) Maximum combined area - same features with max combined areas will be assigned
cell ID
(TRUE/FALSE) On a conformal map projection, the scale is the same in all directions at
any point on the map, That means that measurements of area will always be correct. -
ANSWER-FALSE
On a conformal map projection, at a given location, the scale is the same in all
directions. However, the scale varies at different locations on the map surface. Explain
how this affects the appearance of features drawn on the map surface and why? -
ANSWER-Conformal maps form a grid where parallels and meridians intersect at a right
angle, even though the space between the longitudinal lines differs based with changing
latitudes, this distorts most areas.
According to National Map Accuracy Standards, larger scale maps should have greater
locational accuracy (T/F) - ANSWER-TRUE
ArcGIS can process multiple raster datasets of varying cell sizes. It makes all cells the
size of the smallest cell size and does it's analysis at that cell size (T/F) - ANSWER-
FALSE
Complete Solutions
(True/False) The size of an ArcMap map document will increase significantly as new
data are added because ArcMap stores a copy of each GIS dataset within the map
document. - ANSWER-FALSE
What are two major differences between shapefiles and geodatabases? - ANSWER-
Shapefiles - single layer per datset, no topology, vector, geometry NOT automatically
calculated
Geodatabase - multiple layers per datset, topoplogy, vector and raster, geometry
automatically calculated
What are two major differences between file geodatabases and personal
geodatabases? - ANSWER-Personal - tied to Microsoft; size-limited (2 Gb)
File - not tied to Microsoft; large sizes possible (up to 1 Tb)
How does an enterprise geodatabase differ from a file geodatabase? - ANSWER-
Enterprise geodatabase - DBMS (database management system) linked; multi-user
editing
File - not access-based; proprietary
Define topology - ANSWER-Shape-invariant (unchanging) spatial properties of lines or
polygons such as adjacency, contiguity, and connectedness, often recorded in a set of
related tables.
Raster compression methods may actually result in larger storage than uncompressed
data. Describe how that might happen. - ANSWER-Run-length encoding creates a table
with the value, length of that value, and row of the run. This is very effective for
compressing data with long strings of identical values however in data sets with
constantly varying values run-length encoding can actually create a larger dataset.
Dataset compression is not important today because of cheap storage devices (T/F) -
ANSWER-FALSE
Name two raster data compression methods discussed in class. - ANSWER-Run-length
and value point encoding
What raster dataset property strongly determines the relative effectiveness (percent
reduction in dataset size after compression) of a data compression technique? -
ANSWER-The number of contiguous cells with the same value
, When performing vector to raster conversion of a polygon layer, how does ArcMap
(using the default conversion method) determine a cell value when the cell is comprised
of parts of multiple different polygons? - ANSWER-ArcMap will use the polygon that
crosses the cell center
Why is UTM not a good coordinate system to use for land areas with a predominant
east-west extent? - ANSWER-UTM zones standard parallels run N-S making it good for
mapping areas with the same extent; also if an area has an E-W extent it may cross a
UTM boundary and since each UTM boundary has its own coordinate system, making
analysis difficult
In ArcGIS, as long as you have the map projection correctly specified, you don't need to
worry about datum corrections (True/False) - ANSWER-FALSE
State Plane is a standardized coordinate system that is used by all states so that data
can be shared easily across state boundaries (True/False) - ANSWER-FALSE
When performing vector to raster conversion of a polygon layer in ArcGIS, explain what
options you have to help you control what value will be assigned to a cell that has
multiple features within it. - ANSWER-1) Cell center - feature that crosses cell center will
be assigned cell ID
2) Maximum area - single feature with greatest area will be assigned cell ID
3) Maximum combined area - same features with max combined areas will be assigned
cell ID
(TRUE/FALSE) On a conformal map projection, the scale is the same in all directions at
any point on the map, That means that measurements of area will always be correct. -
ANSWER-FALSE
On a conformal map projection, at a given location, the scale is the same in all
directions. However, the scale varies at different locations on the map surface. Explain
how this affects the appearance of features drawn on the map surface and why? -
ANSWER-Conformal maps form a grid where parallels and meridians intersect at a right
angle, even though the space between the longitudinal lines differs based with changing
latitudes, this distorts most areas.
According to National Map Accuracy Standards, larger scale maps should have greater
locational accuracy (T/F) - ANSWER-TRUE
ArcGIS can process multiple raster datasets of varying cell sizes. It makes all cells the
size of the smallest cell size and does it's analysis at that cell size (T/F) - ANSWER-
FALSE
