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RTCM Compatability
302 5 8-6 07:25
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Tark
lvl.2

United States
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Hi yall,

Been reading a lot of your posts on reproducable accurate mapping. I'm trying to get decent relative reproducable accuracy (doesn't necessarily need to be survey quality, just mostly repeatable) over a relativly large area without hiring a professional surveyor to come out and mark GCP's and check points all over our area of interest. Which I know is the only way to guarantee accuracy. I'm hoping the NTRIP network in my area will mostly fix this, but just like most things DJI they make it sound like all ya do is plug a dongle with a GSM sim card in and away you go, but my only options for mount points are VRS_CMR, CRS_CMRx, and VRS_RTCMv3. The only info I've been able to find on compatability is in the question and answer section here. It's not official from DJI, but it says 3 options with RTK are :
1. Connect locally via OcuSync to your D-RTK 2 Mobile Station. (RTCM3.2)
2. Connect remotely via a 4G Dongle to a custom RTK network using a NTRIP account.(RTCM3.2)
3. Connect remotely via a WiFi hotspot to a custom RTK network using a NTRIP account. Not available in Europe.(RTCM3.0/RTCM3.1/RTCM3.2)"
So does that mean without access RTCM 3.2 the dongle sim card option is useless? Basic background in GIS and spatial analysis, but not surveying. So if anyone has any info on this please explain like I'm 5.


Thanks!

PS. Might as well get opinions on what I'm thinking second option is if this NTRIP doesn't work or doesn't give me the desired end product and can't get the bosses to spend the dough on a surveyor.

At the moment my workflow is setup base station. Take note of and mark on ground where base records location (for manualy entering in lat long during next flight for repeatability) mark a location  towards the end of my flight path, fly area, process images into ortho, use GIS to get lat/long of next "Known location" on my new ortho, place base station over marked location, manually enter lat long in acquired from GIS, and repeat through my area of interest in order to create a relative accuracy to the original base station. So far my tests seem to be atleast matching pretty seamlessly. Haven't even started trying to get dsm's to stitch, so if anyone see's any potential issues this workflow could cause for stitching dsm's I'd love to hear about it. More tests today. I'll update results if there is any interest.
8-6 07:25
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Tark
lvl.2

United States
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https://flyhighusa.com/product/phantom-4-rtk/  link didn't work up top
8-6 07:29
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patiam
First Officer
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United States
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You only need the dongle if you need to connect to an NTRIP source and don't have another way to get online, such as a hotspot from a mobile phone. There may be other modes that use the dongle but so far those haven't been documented well or at all. Your VRS_RTCMv3 NTRIP resource should work as long as you have access credentials. Note that you must enter the name of the mountpoint in the Custom RTK setup on the RC.

If NTRIP is not available, you'll find best results if you place the D-RTK 2 over a point with precisely known coordinates. You should theoretically be able to log data with the D-RTK 2 and then download it and post-process it using a service such as OPUS, but AFAIK nobody has figured this out. So our procedure is to use another RTK-grade receiver to do that, and enter the coordinates in the D-RTK 2 setup.

Your workflow of leap-frogging your base station location by picking coordinates from you map products is going to compound your errors.
8-6 09:52
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Tark
lvl.2

United States
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Thanks patiam. That link I mentioned just made it seem to me like RTCM 3.2 was the only compatible version. I have a pretty high confidence that this NTRIP network will give me the results I require. My associate connects to it with her trimble hand held GPS unit and is able to get 2 foot accuracy while only connected to 7 satellites. I usually get 20-25 connections on the P4RTK so I think I should get a pretty high level of accuracy and reproducibility. My main need is to be able to fly any area, large or small, in my zone of interest and have it layer with as little offset as possible to previous flights of the same area. Just using the base station flying the same area I was getting shifts in the mosaic in feet (setting up over the same spot and manually entering lat/long used from last flight has improved that, but any adjacent ortho's don't line up). But by using my fudged known locations (leap frogging my base station) I was hoping to get at least mostly relative accuracy in small parcels of my larger area. I know it's sloppy, but I gotta work on something to keep me busy while I wait for everything I need for this NTRIP solution. Plus Everytime I go do a test flight I learn something new, Like today I learned that when your RC battery gets low it yells at you in cantonese.
8-6 13:05
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Tark
lvl.2

United States
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Sorry, after a bit of research i believe it was probably Mandarin.
8-6 13:19
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CoastalCapt
lvl.2
Flight distance : 192343 ft
United States
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Tark,

Who runs the NTRIP/VRS network you are planning on using? If that VRS_RTCM3 doesnt work, they may have another IP address/server you can connect to that has other RTCM mount point options.  Hope this helps.
8-7 10:41
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