Ohio State is in the process of revising websites and program materials to accurately reflect compliance with the law. While this work occurs, language referencing protected class status or other activities prohibited by Ohio Senate Bill 1 may still appear in some places. However, all programs and activities are being administered in compliance with federal and state law.

Workflow- Processing Imagery and Tile Caching

Topic:
Enterprise GIS
Tags:
Drone

Overview

This is a guide to taking raw drone data through several steps that will result in an image service using the data.

This is an advanced version of the KB "Generic Postflight Processing in SiteScan".

This should only be necessary on very large flights and the prior KB would suffice for many small flights not requiring a dedicated service or tile cache. 

Most commonly done with the Wingtra and for the Leaf On/ Off Imagery collection of the Columbus Campus.

Step 1. Geotagging

Start by converting images into geographically aware images.

  1. Open Wingtra Hub on the Beast to geotag your drone flights.
    • Download the necessary CORS data (.rinex) from https://cors.dot.state.oh.us/Rinex%2024hrs/Rinex/
  2. In Wingtra Hub, go to the Geotagging tab at the top
    • Navigate to the flight WingtraPilotProjects folder on the SD card and add to Wingtra Hub. *****

Step 2. Process Imagery

It is time to merge 100s of images and create a tiff file (or multiple).

  1. Open Sitescan and create a new project
  2. Upload a images on a per-flight basis
  3. Process the images
    • Output Quality: Ultra
  4. After areas are processed on a per-flight basis, click on Merge Missions
    • Select the check box next to each flight you want to merge, click Merge Missions again. Name your Merged Mission and click on Merge.
      • Columbus Campus - West Campus + Morehouse (Carmenton), Waterman + Kenny Rd (Waterman), Athletics + Vet Med (Mid Campus), Academic Core + Med Center (Main Campus)
        • Autel flights are separate - Waterman Tower and Wetlands Research Area
      • Regionals are merged on an as needed basis
  5. Review the images for issues and reprocess major holes, deformities, etc
    • Review large areas of trees and reprocess to try and get better quality
  6. Download .tiff to the Beast to work on in Pro

Step 3. Clean Tiffs

It is time to combine the data and make it nicer to look at.

  1. Add the handful of merged .tiffs processed to ArcGIS Pro
  2. Use the Copy Raster tool
    • Put the Raster in the same folder as the original.
    • Environments tab:
      • Raster Storage:
        • Build Checked
        • Resampling Technique: Bilinear
        • Compression type: Default
      • Resampling Method: Bilinear
  3. Build Pyramids for each tif. This may automatically be done but this is with the incorrect settings most of the time.
    • Ensure the correct values by rebuilding with:
      • Resampling Technique set to: Bilinear. This is to smooth the "static" look found in nearest neighbor sampling
      • Compression type: default. Not sure of the other types but "no compression" adds a black border to the data.
      • Environments- Parallel Processing on a strong computer speeds up processing time.
    • Doing this may cause a large black boundary on the tif. Try removing this using the symbology pane "mask" tab.
  4. Drag around the unaligned tifs if you used multiple drones for collection with varying x,y accuracy.   
  5. Mask the overlap and clean up borders.
    • Simple masking can be done using a few feature layers and no geoprocessing tools.
    • Ensure masking is an option on the Raster Layer tab within Pro. Select the feature layer you make to omit the overlapped raster data from view.
  6. Move the tifs to be in the order of display (e.g. Med Center/Main Campus is overlapping Vet Med/Middle Campus because the river looks better with that tif)
  7. You do not need to merge the tifs into one to make a cache. You will get a "what you see is what you get". Ensure what you see looks good or else the cache will not. 

Step 4. Create a Tile Cache

A static copy of the data optimized for draw speed needs made. 

  1. Use the Manage Tile Cache GP tool to make a cache.
    • recreate all tiles.
    • run a medium-size layer alone to verify the output looks correct first.
    • It tries to make you select a single tif. You can go to your project and select the whole map. Avoiding the need for a merge of the layers.  
  2. Run all layers
  3. Add the cache to a map and QC it at many locations and zoom levels. Slowly so the project has time to redraw according to the cache.
  4. Move the image cache to the GIS file server following the folder conventions
  5. Remember the location of this cache folder for later. It will be referenced.

Step 5. Create Image Service

Define a service and alter it. 

  1. Make a service using "share web layer". In configuration you should be able to establish a connection to an existing tile cache.
    • If not, rename the folder so the cache is not accessible ie "cachename_temp"
    • publish the service with a dynamic reference to the data.
    • go to server manager and change the reference type to from cache and let it build a folder directory.
    • paste the data in from the temp folder.
  2. Activate the service
  3. paste the correct tiles into the imagery folder directory. 

Step 6. Clean Up

  1. The files created over the course of this need reviewed and consolidated.
    • This process can make hundred of Gigabytes of data if you are not careful.
  2. Raw processed imagery can be discarded if it has not been altered. It can be retrieved later from SiteScan if needed.
  3. Keep the copy of the imagery that you performed the build pyramids and masking on for the current year.
    • Go back a year and delete the previous one, this is only kept in case an issue arises and the cache needs rebuilt to tweak something.