Emlid RS2 Rover and Base workflow

[rossparry (Mellows)]

Good day,

I wanted to reach out and ask a few questions regarding Emlids and Drone based surveying. I’m fairly new to the process and looking to dial in a workflow. I’m not a surveyor by trade, but have been active in the drone capture world for the last 3 years and really looking to improve our data accuracy.

At this time we have two Emlid RS2 units (looking to upgrade to a RS3 and RX), and would like to utilize them with a DJI M300 and M350. This prior work week we have been in the field and have managed to log our base point, send out our RINEX data and have it corrected, shoot 5 GCP’s and have flown a few Ortho flights.

A few questions for you.

When setting up our base (not on a known point) I see the option to enter the antenna height in the logging window. Would you recommend having that height marked in the Emlid Flow app logging section before we start our 1-4 hours of averaging to get our correction? Where we perform our work, we don’t have access to NTRIP or may be quite far from a survey monument.

Secondly, our M300/350s all utilize WGS84. When creating our initial project in Emlid Flow, I made the mistake of using NAD83(CSRS) / UTM zone 11N instead of WGS84 / UTM zone 11N. Our GCP’s were nowhere near our base when checking the data in PIX4D. When the project is created using the WGS 84 coordinate system, will this be applied to the base unit Emlid or will a conversion be required and shall we collect the base data in the correct NAD83 format?

Any insight/help would be greatly appreciated. We are looking to create a workflow utilizing the tools we have.

Thank you.

[dpitman (Dave Pitman)]

@rossparry

When setting up our base (not on a known point) I see the option to enter the antenna height in the logging window. Would you recommend having that height marked in the Emlid Flow app logging section before we start our 1-4 hours of averaging to get our correction?

If you want the coordinate to the point on the ground, then you need to enter the pole height. Otherwise, your coordinate will be the phase center of the receiver at the top of the pole. I doubt you want that.

@rossparry

we don’t have access to NTRIP or may be quite far from a survey monument.

You don’t have access to NTRIP, but you are “having it corrected” which I assume you mean through a PPP service like OPUS. And then using the corrected point as the base point to set your ground control. That is all fine. Just remember to also specify the pole height in that PPP service. OPUS, for example, does not read the pole height from the uploaded file. You have to specify it manually.

@rossparry

Secondly, our M300/350s all utilize WGS84. When creating our initial project in Emlid Flow, I made the mistake of using NAD83(CSRS) / UTM zone 11N instead of WGS84 / UTM zone 11N. Our GCP’s were nowhere near our base when checking the data in PIX4D. When the project is created using the WGS 84 coordinate system, will this be applied to the base unit Emlid or will a conversion be required and shall we collect the base data in the correct NAD83 format?

There are different approaches to deal with going from geographic (wgs84) to projected (UTM 11N) that all work. What I do for simplicity is to do all of the work with the drone and photogrammetry in wgs84 and then transform to another CS afterwards if needed. You can also do transformations anywhere in the process, but it is a little bit more tricky. So you need to have a good grasp of what is happening.