After uploading your data to PrecisionMapper our processing engines stitches your individual pictures together to develop georeferenced 2D and 3D outputs in several file formats. Certain outputs will be viewable in the PrecisionMapper web viewer while others may need to be downloaded from the site to analyze in other software. To understand the technical details of each output type and where to view them see the PrecisionMapper Outputs section of the knowledge base. Also make sure to take a look at our Exporting 2D and Exporting 3D output articles for an understanding of how to open this data outside of precisionmapper.com.
Below we have reviewed some strategies to making this data useful in your analysis. We are using QGIS and the Quick Terrain Reader software for this analysis.
Overlay 2D Outputs
Overlaying multiple sources of 2 Dimensional outputs can be extremely useful in analysis and visualization of your data. In this example we will show you how to overlay your Volume shapefile output on your original orthomosaic. This same idea can be used to overlay any output from PrecisionMapper within QGIS.
The ability to overlay unlimited sources of geospatial data really only scratches the surface of functionality in QGIS. For a full review of capabilities in the QGIS software be sure to check out their tutorials page- https://www.qgistutorials.com/en/
1. Using the workflow explained in the Exporting 2D Outputs article open the Tiff output of your orthomosaic in QGIS.
2. Now that you have the Orthomosaic opened in QGIS you have full zoom capabilities for simple viewing of your orthomosaic. If you would like to take it a step futher you can also overlay related datasets in the software.
3. In this example I am adding my Volume Estimation shapefile layer onto the QGIS map. The Shapefile is considered a “Vector” layer so this time I will go into “Layers” in the main tool bar- “Add Layer”- “Add Vector Layer”.
4. Shapefiles are made of several connected file types. So when you navigate to this to add the layer you will see a package of files within your shapefile output. Select the version that has .shp file type to get this added to your data frame.
5. Once you have opened this shapefile it should overlap on top of the data currently in QGIS. If it does not you can use the “Layers Panel” on the right side to re order the layers deciding which appears on the top of the overlay.
Vegetation Indices in QGIS
In our online viewer our Vegetation Index maps will show you a relative range of plant health values from Green to Red. Some users are required to edit how these values are represented by changing the color ramp in QGIS. This allows the user to customize the visualization in their maps to prove or dis prove some disruption in the field.
In this section we will go over how to edit the color ramp in QGIS and threshold values to emphasize particular values in the vegetation index output.
1. Using the GeoTiff output of the Vegetation Index open the Raster file within the QGIS software.
2. Once you have this opened you will first notice that the coloration of the file is very different from the online viewer. All the same values are present but the color ramp assigned to these values is Black to White instead of Red to Green.
3. You are able to change the color style of this map by changing the “Properties” of the layer. To do this right click on your layer in the “Layers Panel” on the left side, go to “Properties”, and go into the “Style” menu.
4. Under “Render Type” you can select “Singleband Pseudocolor” in the drop down. From here you will be able to alter the color ramp associated with the dataset. Within the “Load Min/Max Values” section there is a “Color” setting that you can change to any color scale you like. In my example I am changing it to a similar Red to Green style seen in the PrecisionMapper viewer.
5. To customize the visualization further we will threshold the values of the vegetation index. This will allow us to emphasize the location of the living plant matter in the vegetation index. Currently my vegetation index output has values from -0.185234 to 0.401612. It seems like all pixels representing living vegetation are > 0.
6. Go back into the "Properties" of the Vegetation Index layer you are working with and go to the "Symbology" tab again.
7. At the top of the Symbology menu you will see a Min and Max value. Since the lower value pixels represent the "Non Living" material in the survey we want to edit that Min value. In this case we are changing it to 0.
By changing this minimum value we transform the look of the vegetation index output to emphasize the trees in the survey.
9. Now to allow for further enhancement of the trees in this vegetation index output we will use the "Clip out of range values" check box in the Symbology tab. This will make all pixel values outside of the Min-Max range have no color at all.
This version of the vegetation index output would be particularly useful to manually count the trees or study the health of just the trees without the background noise of ground pixels in the VI output.
Analyzing 3D Data in Quick Terrain Reader
The 3D outputs of the PrecisionMapper can be very useful for analysis of terrain or buildings. Within precisionmapper.com you can view the 3D model output of your project if 3D outputs were selected during the upload process. This is a simple view of your dataset with elevation values accounted for in the 3D view.
To gain a little more functionality from your 3D outputs you may consider pulling the data to an external software can be useful. We have already covered how to open 3D output files in the Quick Terrain Reader software within our Exporting 3D Outputs article. Now we will dig into some of the Quick Terrain Reader tools that you could use in further analysis of your 3D data.
- The “Model Information” tool can give you a quick view of the elevation distribution in your dataset along with other useful statistics. Choose the Model Information Icon from the main tool bar to view this report-
- The measurement tool can be used to measure horizontal and vertical distances between features in your 3D view of the data. To use this feature you will select the “Start Mensuration” tool from the main tool bar. Click on the start and end points of what you want to measure and you will see a distance appear at the top of the measuring bar within the viewer.
- To explore more features within Quick Terrain Reader check out their tutorials page- http://appliedimagery.com/tutorials/