Advanced Topics |
This section will cover topics that were not covered in the Introduction to Digital Mapping (CIT 125), to give the learner more tools to use in geospatial technology. http://introductiontogist.weebly.com/ The learner can select a software platform which include ArcGIS Desktop, ArcGIS Pro or QGIS. The functional geoprocessing names may vary by platform. The topics in this Case Study/Lesson were done using ArcGIS Pro.
Topics
Intersection:
http://pro.arcgis.com/en/pro-app/tool-reference/analysis/intersect.htm
An Intersection is the process of using two or more feature files that overlap and determining the common elements, a new file of only the common elements will be created. If the files are of different geometries then the lowest geometry will be the default, i.e. such as polygon and line the output will be a line. multiple items of different feature types can be inputted together. Select two or more input files initially of the same type. Intersection is under the Analysis tab. Input the files to be used to find the intersection and provide an output file name.
Union:
http://pro.arcgis.com/en/pro-app/tool-reference/analysis/how-union-analysis-works.htm and
http://pro.arcgis.com/en/pro-app/tool-reference/analysis/union.htm
A Union is the process of combining common features of polygon geometries. For example if two items have overlaps but not inclusive, then the output would include all features. In general the geometries will have overlap. Select two or more input files that have some amount of overlap but are not inclusive. Union is under the Analysis tab. Make sure an appropriate output file name is used for the created feature.
Near:
http://pro.arcgis.com/en/pro-app/tool-reference/analysis/near.htm
Near is a statistical calculation of how close different objects are located. When this geoprocessing tool is used, it will create new columns in the input feature file, which will include a Near-Dist field. The comparison on distance can be used for items within the input feature or another point/line/polygon feature. A search radius is given for the 'nearness to be calculated', the units can be angular or distance, thus a projection is required. The near geoprocessing tool is under the analysis tool in the tools window.
For example if you want to determine how close hospitals are to each other in a state, the Near tool can be used, the input would be the location of the hospitals and new feature would also be the hospitals. The near-dist field will be shown using a graduated symbology for symbols. Thus those hospital near to one another will have much smaller diameter symbol then those farther apart.
Dissolve:
http://pro.arcgis.com/en/pro-app/tool-reference/data-management/dissolve.htm
Dissolve provides the ability to combine small areas into a large area. For example if you have a census tract file of an entire state and would like to know the population of each race at the county level instead of the tract level, this process can accomplish this. If the feature file contains a county name with each census tract, then the race fields at the census tract level can be dissolved into the race at the county levels and would only have the number of rows for the number of counties in the state and the field would only be for the different races, assuming that was all that was selected. Select a file that has two different levels of divisions, like census tract and counties or counties and a state. A new file will be created and good naming conventions is really important. Dissolve is under the Analysis tab.
Append:
http://pro.arcgis.com/en/pro-app/tool-reference/data-management/append.htm
Append is the process of combining multiple information sources into a single non-duplicated feature. For example if you have rivers files for two different streams in an area, you can append these two files together to create a single feature file for both rivers. The input fields must match, if not the Field Map tool in this geoprocess must be used. Multiple files of the same type, i.e. rivers, roads, etc., can be used. The Append command is located in the Analysis tab.
Kernel Density:
http://pro.arcgis.com/en/pro-app/tool-reference/spatial-analyst/how-kernel-density-works.htm and
http://pro.arcgis.com/en/pro-app/tool-reference/spatial-analyst/kernel-density.htm and
https://www.calculator.net/standard-deviation-calculator.html or
https://www.calculatorsoup.com/calculators/statistics/statistics.php
Kernel Density is a statistical process to display information that shows how tightly packed the data. Through the statistical equations a raster image can be constructed to show how close multiple data points are to each other. Note that use of the word density in this format is not the physics definition of mass per volume, but deals with a concentration per an area. This process will also work with line features. There are many other ways to determine density of items used in geospatial technologies and are part of the tool set in geoprocessing.
Several statistical terms are used in this concept and it is suggested that you might review the National Geospatial Technology Center of Excellence concept module on Statistics Part I located at: http://www.geotechcenter.org/statistics-part-1.html . Mean is the average which is determine by summing values and dividing by the number values, Mode is the most common value with the same numeric value, and Median is the central point of the data set. Standard deviation is how close the data points are together, the smaller the value of the standard deviation value the closer packed are the data points. One standard deviation represents how close 68% of the data is to the mean. For more information see: https://simple.wikipedia.org/wiki/Standard_deviation
For example if 11 values were 20, 25, 25, 30, 40, 40, 40, 50, 65, 90, 100; the sum is 525, the mean is 47.7, median is 40 and mode is also 40, with a standard deviation of 26.68.
The Kernel Density process is located under the Analysis tab in the tools window. Once the process has been selected, the geoprocessing window will open on the right side of the map. Input a point feature that has closely aligned points. For the population field, you can select None or a field that contains population values, for this case select None. A new raster layer will be constructed and select an appropriate name. For the pass leave all other items with their default values, the learner can modify these in the future. The raster layer should automatically be added to the map. The output Value will be the population density, note each point was used with a value of 1, since the population field was set to none. There are other statistical methods that can also be used to view data.
Metadata:
https://www.fgdc.gov/resources/factsheets/documents/GeospatialMetadata-July2011.pdf and
http://pro.arcgis.com/en/pro-app/help/metadata/view-and-edit-metadata.hwww.geotechcenter.org/metadata.html and
http://www.geotechcenter.org/metadata.html
Metadata is data about the data. The command is located in the layer property window, which is addressed by double clicking on a layer. A single feature file is required. Select a layer file and input metadata about the file. Use the pull-down and select 'Layer has its own metadata'. Next use the copy icon which should be visible, by selecting this icon it will allow for information to be loaded. Finally enter additional metadata for the layer. When completed click okay to save the metadata.
Projections:
http://pro.arcgis.com/en/pro-app/help/mapping/properties/coordinate-systems-and-projections.htm and http://desktop.arcgis.com/en/arcmap/latest/map/projections/what-are-map-projections.htm
It is suggested that the section on map projections from the introductory class be reviewed, http://introductiontogist.weebly.com/ also consult the Concept Module of the National Geospatial Technology Center of Excellence at http://www.geotechcenter.org/map-projections.html. A projection is used to take the three dimensional surface of the earth and create it into two dimensional model that can be used for mapping. There are many different projections that can be used but the proper one must be selected for the location. If data is not projected it cannot be used for accurate measurements and placements. In addition some geoprocessing tools will not work such as near and buffering.
There are several different coordinates but in general they are either angular (such as longitude and latitude) or distance measurements for the x, y plane. The z plane is generally a distance measurement. Generally today with angular coordinate systems are used decimal degrees are used. The projected data can be changed from one coordinate system to another by use of transformations which are mathematical calculations.
Provide your instructor with different examples of projections and coordinate systems.
http://pro.arcgis.com/en/pro-app/tool-reference/analysis/intersect.htm
An Intersection is the process of using two or more feature files that overlap and determining the common elements, a new file of only the common elements will be created. If the files are of different geometries then the lowest geometry will be the default, i.e. such as polygon and line the output will be a line. multiple items of different feature types can be inputted together. Select two or more input files initially of the same type. Intersection is under the Analysis tab. Input the files to be used to find the intersection and provide an output file name.
Union:
http://pro.arcgis.com/en/pro-app/tool-reference/analysis/how-union-analysis-works.htm and
http://pro.arcgis.com/en/pro-app/tool-reference/analysis/union.htm
A Union is the process of combining common features of polygon geometries. For example if two items have overlaps but not inclusive, then the output would include all features. In general the geometries will have overlap. Select two or more input files that have some amount of overlap but are not inclusive. Union is under the Analysis tab. Make sure an appropriate output file name is used for the created feature.
Near:
http://pro.arcgis.com/en/pro-app/tool-reference/analysis/near.htm
Near is a statistical calculation of how close different objects are located. When this geoprocessing tool is used, it will create new columns in the input feature file, which will include a Near-Dist field. The comparison on distance can be used for items within the input feature or another point/line/polygon feature. A search radius is given for the 'nearness to be calculated', the units can be angular or distance, thus a projection is required. The near geoprocessing tool is under the analysis tool in the tools window.
For example if you want to determine how close hospitals are to each other in a state, the Near tool can be used, the input would be the location of the hospitals and new feature would also be the hospitals. The near-dist field will be shown using a graduated symbology for symbols. Thus those hospital near to one another will have much smaller diameter symbol then those farther apart.
Dissolve:
http://pro.arcgis.com/en/pro-app/tool-reference/data-management/dissolve.htm
Dissolve provides the ability to combine small areas into a large area. For example if you have a census tract file of an entire state and would like to know the population of each race at the county level instead of the tract level, this process can accomplish this. If the feature file contains a county name with each census tract, then the race fields at the census tract level can be dissolved into the race at the county levels and would only have the number of rows for the number of counties in the state and the field would only be for the different races, assuming that was all that was selected. Select a file that has two different levels of divisions, like census tract and counties or counties and a state. A new file will be created and good naming conventions is really important. Dissolve is under the Analysis tab.
Append:
http://pro.arcgis.com/en/pro-app/tool-reference/data-management/append.htm
Append is the process of combining multiple information sources into a single non-duplicated feature. For example if you have rivers files for two different streams in an area, you can append these two files together to create a single feature file for both rivers. The input fields must match, if not the Field Map tool in this geoprocess must be used. Multiple files of the same type, i.e. rivers, roads, etc., can be used. The Append command is located in the Analysis tab.
Kernel Density:
http://pro.arcgis.com/en/pro-app/tool-reference/spatial-analyst/how-kernel-density-works.htm and
http://pro.arcgis.com/en/pro-app/tool-reference/spatial-analyst/kernel-density.htm and
https://www.calculator.net/standard-deviation-calculator.html or
https://www.calculatorsoup.com/calculators/statistics/statistics.php
Kernel Density is a statistical process to display information that shows how tightly packed the data. Through the statistical equations a raster image can be constructed to show how close multiple data points are to each other. Note that use of the word density in this format is not the physics definition of mass per volume, but deals with a concentration per an area. This process will also work with line features. There are many other ways to determine density of items used in geospatial technologies and are part of the tool set in geoprocessing.
Several statistical terms are used in this concept and it is suggested that you might review the National Geospatial Technology Center of Excellence concept module on Statistics Part I located at: http://www.geotechcenter.org/statistics-part-1.html . Mean is the average which is determine by summing values and dividing by the number values, Mode is the most common value with the same numeric value, and Median is the central point of the data set. Standard deviation is how close the data points are together, the smaller the value of the standard deviation value the closer packed are the data points. One standard deviation represents how close 68% of the data is to the mean. For more information see: https://simple.wikipedia.org/wiki/Standard_deviation
For example if 11 values were 20, 25, 25, 30, 40, 40, 40, 50, 65, 90, 100; the sum is 525, the mean is 47.7, median is 40 and mode is also 40, with a standard deviation of 26.68.
The Kernel Density process is located under the Analysis tab in the tools window. Once the process has been selected, the geoprocessing window will open on the right side of the map. Input a point feature that has closely aligned points. For the population field, you can select None or a field that contains population values, for this case select None. A new raster layer will be constructed and select an appropriate name. For the pass leave all other items with their default values, the learner can modify these in the future. The raster layer should automatically be added to the map. The output Value will be the population density, note each point was used with a value of 1, since the population field was set to none. There are other statistical methods that can also be used to view data.
Metadata:
https://www.fgdc.gov/resources/factsheets/documents/GeospatialMetadata-July2011.pdf and
http://pro.arcgis.com/en/pro-app/help/metadata/view-and-edit-metadata.hwww.geotechcenter.org/metadata.html and
http://www.geotechcenter.org/metadata.html
Metadata is data about the data. The command is located in the layer property window, which is addressed by double clicking on a layer. A single feature file is required. Select a layer file and input metadata about the file. Use the pull-down and select 'Layer has its own metadata'. Next use the copy icon which should be visible, by selecting this icon it will allow for information to be loaded. Finally enter additional metadata for the layer. When completed click okay to save the metadata.
Projections:
http://pro.arcgis.com/en/pro-app/help/mapping/properties/coordinate-systems-and-projections.htm and http://desktop.arcgis.com/en/arcmap/latest/map/projections/what-are-map-projections.htm
It is suggested that the section on map projections from the introductory class be reviewed, http://introductiontogist.weebly.com/ also consult the Concept Module of the National Geospatial Technology Center of Excellence at http://www.geotechcenter.org/map-projections.html. A projection is used to take the three dimensional surface of the earth and create it into two dimensional model that can be used for mapping. There are many different projections that can be used but the proper one must be selected for the location. If data is not projected it cannot be used for accurate measurements and placements. In addition some geoprocessing tools will not work such as near and buffering.
There are several different coordinates but in general they are either angular (such as longitude and latitude) or distance measurements for the x, y plane. The z plane is generally a distance measurement. Generally today with angular coordinate systems are used decimal degrees are used. The projected data can be changed from one coordinate system to another by use of transformations which are mathematical calculations.
Provide your instructor with different examples of projections and coordinate systems.