The following step-by-step instructions demonstrate how WingtraOne PPK projects can be processed in your custom grid coordinates without using ground control points (GCPs). The WingtraOne images are geotagged using WingtraHub (WiH). For further processing, the description is tailored to Propeller Aero. If you are not using PPK for Wingtra, simply upload the geotags using WGS84 EGM96, and use ground control to correct the model.
For information about Wingtra PPK geotagging process, please review the article called PPK geotagging. Propeller has an article for Uploading high-accuracy geotagged photo datasets to use as a resource guide.
It is important to note that WiH can process geotags in WGS84 and NAD83(2011). Most OPUS or CORS reports provide coordinates in NAD83(2011). If you use this method, you will need to convert the base point given in NAD83(2011) into WGS84, because Propeller works best when the geotags are provided in WGS84 coordinates. IGS08 coordinates sometimes do not convert correctly when imported into the Propeller. Link to public NGS converter.
Section 1: correcting Aeropoint or ground check point position
Once your Aeropoints have been uploaded to the cloud via hotspot, you will see the points uploaded under the Aeropoints tab. If no Aeropoints were used, proceed to section two and three, which will be the case if you are using your own survey collection equipment.
Step 1: specify what method you will use to correct the positions of the Aeropoints. Most of the time, this will be set up over a local site benchmark for a custom coordinate system. If the coordinate system is published, select the global survey benchmark. If no benchmarks are present, try to correct based on the same base station as Wingtra. Click process once the point location is specified. NOTE: If you use the RINEX method to correct the Aeropoints, make sure it is using a file which has been post-processed; otherwise, there will be a mismatch between the corrected Wingtra geotags and Aeropoints referencing an uncorrected RINEX file.
Tip for local coordinates: The propeller Aeropoint can’t be used as a base station to correct our images, so if you are working in a custom local site, we suggest setting up the Aeropoint on a known control point and the base station on a separate known point. You can set both over the same point, but remember to add a 33 mm or .108268 ft offset in WingtraHub for the thickness offset of the Aeropad. Also, be sure to use the Aerostencils to center the pad perfectly over the control point. Having the base station and Aeropoint on separate control points is preferred so there is no obstruction on the Aeropoint.
Step 2: download the Aeropoints, or move forward with uploading images for processing in Propeller.
Step 3: review the Aeropoint positions and accuracy.
Section 2: creating and processing your project
Step 1: name the site and specify the industry.
Step 2: enter the site location and align the map.
Step 3: set up the site’s coordinate system using the local grid system then import the JXL file. If you do not know how to get the JXL file, follow the instructions in this link: http://help.propelleraero.com/en/articles/999288-how-to-generate-a-trimble-jxl-file-for-your-local-grid-calibration.
If you want to view the calibration and enter a test point, you may try that here under Check transformation.
Step 4: invite people to your site.
Step 5: upload the data.
Section 3: uploading Wingtra images
Step 1: click on the survey for submitting data.
Step 2: drag in the Wingtra images that have been geotagged using WGS84 coordinates. If you are using PPK, make sure to right-toggle the option so that the images are PPK high accuracy.
Step 3: enter the details of the dataset.
Step 4: specify how you are importing the ground control. You can import CSV files collected from survey equipment—Aeropoints, both, or none. If you wish to use the GCPs to help the model, try to use 3 -5 that are evenly spaced because using 1-2 without balance could skew the model. For PPK, if you do not use GCPs to influence the model, we then must specify that the targets are checkpoints not intended for processing, but rather for accuracy validation. You can do this by selecting the no GCP option after importing the points or toggling them off for processing.
You can view the imported vertical system of the high accuracy geotags and toggle the control points.
If you want to let the image processor know the most accurate processing settings in the comments, specify what the mean accuracy of the geotags are based on the WingtraHub report in the OUTPUT folder.
Step 5: configure the deliverables you wish to be created.
Step 6: verify that all the information in the settings is correct.
Section 4: analyzing the results
Create a point of interest and identify where the aerial target is to mark the position. Compare the interest point location and the position of the processed position to determine accuracy.
For a more detailed analysis, under files, download the processing report. If you changed your control to checkpoints then it will be a fair comparison of the accuracy of the model.