I am not a surveyor and the facet L band is the first rover/base ive used. I’m struggling to figure out why my elevation data is 103 foot low when i take it out to a county survey monument to check for accuracy. I setup the pointperfect just like sparkfun showed in the setup video and i’m using SWmaps. There must be a setting i’m not activating somewhere, the horizontal location seems very accurate. Signal is strong on the L band display. SIV has three bars on the dish thing and less than .03on the hpa. Keys are current. thanks in advance for any help
Russel has again beat me to a solution, but I thought I’d add some context, given that our tutorial is packed full of dense information. The ZED-F9P receiver in the Facet outputs both ellipsoid altitude and MLS altitude, using the WGS84 reference frame. SW Maps displays ellipsoid altitude. Most survey monuments in North America are made using the NAD83 reference frame, and I believe the elevation they depict is always in MSL.
The link Russel provided goes extensively in depth with all of this. Please let us know if this tutorial solves your problem or if you need more information. Also, feel free to send me a private message with the survey monument ID and the coordinates you measured; I could do the conversion on my side as well, and we could compare outputs.
Thanks for the tips, I’ll give these a try today. I also added a geoid file to SW Maps last night that i would like to go back to the monument and see if that makes any changes today. I’ll post any results.
I setup Ntrip through rtk2go. But turns out there are no casters close, i think the closest is around 500 miles away so i don’t think that will help much.
Do i need to set up a THING account for point perfect? The tutorial from sparkfun on that seemed way too easy, and when i go to the website to set up an account it says nothing about the 12 months free that comes with the Lband facet. It only wants me to buy 12 months. My understanding was point perfect was the key to vertical accuracy without a base, but i really cant tell if i’m actually connected to it.
Thanks for the tips, I’ll give these a try today. I also added a geoid file to SW Maps last night that i would like to go back to the monument and see if that makes any changes today. I’ll post any results.
I’ve seen that SW Maps supports Geoid, but haven’t actually tried it out yet. Would love to know how well that worked for you.
Do i need to set up a THING account for point perfect? The tutorial from sparkfun on that seemed way too easy, and when i go to the website to set up an account it says nothing about the 12 months free that comes with the Lband facet. It only wants me to buy 12 months. My understanding was point perfect was the key to vertical accuracy without a base, but i really cant tell if i’m actually connected to it.
No, you don’t need to setup an account with Thingstream. The Facet L-Band comes provisioned with a Thingstream account that activates the first time you use their service, and SparkFun does the work of setting up that account and provisioning. I think the idea here is that actually registering for the service and getting the device provisioned was a really involved task, requiring hardware ID’s, MAC addresses, decryption keys stored on device, etc, so why not automate that on our end, and users can just turn the thing on and start recording.
RTK2Go (and similar NTRIP Casters) and PointPerfect both have the same role; get corrections to your device so it can get an RTK Fix. The two big differences are coverage and methodology; RTK2Go operates over the internet as a relay for RTCM corrections from other base stations, while PointPerfect is a hybrid PPP-RTK that sends corrections via satellite. If you disconnect the Facet from all NTRIP Casters, and get an RTK Fix or Float, you are using PointPerfect corrections. Whether that is more accurate depends on a lot of factors, like which service is used in which location. In my opinion, the best thing about using PointPerfect is that it will work in areas where there is no cell service.
Regarding the original issue with the vertical elevation being off by 103 feet, I have experienced a very similar issue and am researching options. The links in the earlier reply posts did provide a little insight, although I am not sure what the particular answer or reason for the difference really is.
My RTK Fix is WISCORS (WI Base Station Network) and I am consistently seeing elevation differences around 110 feet. I am using SWMAPS and did see that there is an option to include a geoid file although my past experience with base station networks is that the geoid file isn’t needed. Also, the rod height was taken into consideration at time of setup.
Based on the earlier replies it seems that the difference might be in the ellipsoid elevation output in the WGS84 reference VS. the known elevations in NAD83 in Mean Sea Level? If so, how do I configure it so that the data being recorded is in the same format? The X,Y has been working phenomenally well!
