Geospatial Basics

Introduction to Geospatial Data

What makes data geospatial? That is, what makes the data you worked with today geospatial in nature (think coordinates)?

Geospatial data is a type of data that tells the location of something, in most use-cases on earth. This includes, as will be demonstrated later in lab, coordinate systems. Latitude and longitude are also common forms of depicting a position on earth.

What makes data in a GIS different than a digital map?

Digital maps can and often do include coordinates, and sometimes even different coordinate systems. What makes data different in a GIS is the inclusion of attribute data such as elevation.

Why is having an understanding of geospatial concepts and geospatial data so fundamental to working with UAS data?

Unmanned Aerial Systems can collect an immense amount of geospatial data. One of their main uses is in fact collecting and distributing said data. Knowledge of geospatial data is fundamental to working with UASs because many parts of any job related to UASs will utilize geospatial data.

What are some of the key geospatial concepts and fundamentals that this lab addresses?

This lab addresses many different geospatial concepts. The topics covered range from geospatial data files and their formatting, to specific file types, to coordinate systems and metadata. 

Lab Assignment

Working with the Data

Open the Tornadoes folder and find the Tornado_tracks files. List out each file with its extension.

• TORNADO_tracks.dbf
• TORNADO_tracks.prj
• TORNADO_tracks.sbn
• TORNADO_tracks.sbx
• TORNADO_tracks.shp
• TORNADO_tracks.shp XML Document
• TORNADO_tracks.shx

Figure 1: All the file types for TORNADO_tracks

Why is file management so key in working with UAS data?
The sheer number of files can be incredibly overwhelming. Without proper file management files will easily get lost, or forgotten which would cause the layer to not load properly in the GIS software.

ArcCatalog

What is the purpose of establishing a folder connection?

Ease of access to the important folders that will be used.

Figure 2: File condensing in ArcCatalog

Why is the difference between viewing the files in ArcCatalog vs Windows Explorer?

Only the .shp file type is being shown in ArcCatalog, as opposed to the seven file extensions that are shown in Windows Explorer.

Why is it so important, beyond maintaining proper file management/naming, to use ArcCatalog for managing your GIS data?

ArcCatalog makes viewing files much easier, only being shown the .shp files makes navigation much easier. All of the different file types visible in Figure 1 contain data, all of which is included in the shapefiles seen in Figure 2. 

What do those icons mean? Hint: Use the preview tab to view the file

The icons show the type of geospatial data being shown, each type being listed in the next question.

List out each of the geospatial data types, and then provide an example file for that data type.

• Line: TORNADO_tracks
• Point: dams00x020
• Polygon: hucs00p020
• Raster: 20170613_dsm_shd

What topic/term relates to this description tab?

The description tab includes all the metadata for the file.

Why is having this information so important in the UAS realm?

Metadata includes all the important information a file has. Altitude, elevation, date, time, specific coordinates, and so much more can be included as metadata depending on what is being measured, Without metadata, the files have no meaning.

What does it say?

"Band_1 Statistics have not been calculated."

What types of tasks rely on statistics?

Many tasks in ArcMap rely on statistics. Analyzing elevation data, or any imagery really, requires statistics to make sense. 

List the Min, Max, and Mean elevation of the DSM.

• Min: 281.04708862305
• Max: 323.08865356445
• Mean: 296.9669108356

Why would this information be important for data processing, analysis, and communication with the client? (Think of what was discussed in lecture/demo)

A client would want this information to make sense of the data they are seeing. Knowing that one point is higher than another can be done rather easily, but knowing how much higher it is can be a more difficult task that they would want. These statistics can also be compared to past surveys to see the changes in a landscape over time.

• Cell Size: 0.02077, 0.02077
• Format: TIFF
• XY Coordinate System: WGS_1984_UTM_Zone_16N
• Linear Unit: Meter (1.000000)
• Datum: D_WGS_1984
• Use the Linear unit and write the pixel size in square cm: 4.313929 cm^2

ArcMap

Referring to your notes from the demo/lecture, list out some different ways to add data.

• Drag data in from the catalog shown on the right side of ArcMap
• Use the "Add Data"  button on the toolbar
• Go to File > Add Data

What basemap did you use? Why?

World Topographic Map because it was a familiar basemap, and includes the information needed to complete the lab.

What type of GIS data is this? Justify your answer. (Referring to States.shp)

Figure 3: States.shp Polygon Shapefile

Shapes.shp is a polygon shapefile. This is known because the file information lists the shape as polygon, and because the icon shown is the one used for polygon data

Figure 4: Identify tool used on States.shp

What type of GIS data is this? Justify your answer. (Referring to TORNADO_tracks.shp)

TORNADO_tracks.shp is a polyline shapefile. Again, this is known by the icon shown for the file, and can be found with the identify tool.

Figure 5: TORNADO_tracks.shp Polyline Shapefile

What type of GIS data is this? Justify your answer. (Reffering to dams00x020.shp)

dams00x020.shp is a point shapefile. Just as the last two, this can be determined through the file's icon, and through the identify tool.

Figure 6: dams00x020.shp Point Shapefile

Write down the Coordinate System:

• Tornados
• Geographic: GCS_North_American_1983
• Projected: NAD_1983_UTM_Zone_16N
• Dams
• Geographic: GCS_North_American_1983
• Projected: No projected coordinate system is listed
• States
• Geographic: GCS_North_American_1983
• Projected: USA_Contiguous_Equidistant_Conic

Are all of these coordinate systems the same? Why might than be an issue?

All three data layers use the same geographic coordinate system, but not the same projected system. This could be an issue because when using different projected systems, data could be distorted in different ways causing the data points to not appear where they should if the correct projected system was used.

How might the need for metadata relate to coordinate systems?

The metadata available in a file can help decide what coordinate system would be best for the data. Different types of coordinate systems treat the data differently, and the metadata can help the user choose which system is best for illustrating the data most accurately for their purpose.

Think of some different types of attribute data that could be used in conjunction with UAS data and list it here with a use example.

Location and elevation are two of the most important types of data that can be collected by an unmanned system. The elevation of the UAS above ground is also very important. If future surveys are performed, knowing the elevation AGL of the UAS can ensure that the new survey is at the same height AGL so the surveys are easily comparable.

The following questions refer to the Wolfpaving orthomosaic.

• What type of data is this? Raster integer
• What is the format? .tif
• What is the projection? WGS_1984_UTM_Zone_16N

The following refer to XYWOLF_PAVING_UTM16_massaged.shp

• What is the projection? WGS_1984_UTM_Zone_16N
• Does this projection match the Ortho? Whys is this so important? The projection does match. This is important because if the projections are different the data could end up distorted and not line up properly with the orthomosaic.
• Do the points line up with the markers on the ground? Yes, they points and markers line up.

Measure: Measure several features on the map. How might this type of tool be useful in working with UAS data?

The measure tool can measure distances, areas, and features. This can be very helpful to measure distances between two points of which the distance is known to ensure the scaling of the projection is correct, and that points haven't been distorted at all.

Figure 7: Measurement between two GCPs

Identify: Use the identify tool on several of the GCP points. Also, utnr on the DSM and identify pixels on that layer. How might this tool come in handy when working with UAS data?

As has been shown in questions above, the identify tool can provide helpful metadata for specific data points. 

Figure 8: Identify tool used on a GCP

Swipe: Use the swipe tool to move between the Orthomosaic and the DSM. How might this tool be useful when working with UAS data?

The swipe tool can be used to easily and quickly compare the orthomosaic and digital surface model of a surveyed location. 

Figure 9: Swipe tool being used on the Wolpaving data between the orthomosaic and DSM

Conclusions

UAS data is incredibly useful to GIS users because of the capabilities of the systems being used, and the sheer amount of information that is tracked with UASs. The data can be analyzed and manipulated in many different ways to see, for example with the tornado data, where they typically form, how far and fast they travel in different parts of the country, the direction they typically head, and much more. The data is looking at things that have happened, but can very easily be used as a representation of what could happen in the future. There are limitations to this data, however.  If the data spans too much physical space on earth, the projections can lead to distortion of the visualization of the data and not accurately represent the data. Or if the coordinate system being used in the first place is wrong then the data will make no sense. In a previous internship geospatial data was used in a variety of different ways. Storm sewer and water detention basin information were collected and analyzed this way. Townships could utilize geospatial and UAS data to keep track of maintenance and improvement records for houses and their land to ensure that the proper amount of drainage exists at a home to help reduce both the chance for flooding and a potential flood's impact on a property.