Emlid in UK for survey: accuracy/post processing questions

[chiz]

Hi all, looking at getting a Reach RS+ base and rover for archaeological survey work in UK and have a few questions.

I’d mostly be surveying excavation trenches and structures. Spot heights, extents, baselines etc. How easy is it to set up codes for types of point?

Most sites I would be there for at least half a day so could set up base station straight away. Most sites will not have accurately georeferenced survey points, and many won’t have good mobile covereage, let alone mobile internet. What would be the options for getting towards centimetre accuray? Base station will generally be no more than 100m from Rover.

I’ve looked at ‘Ways to set the base’, is ‘Post-Processed Kinematic’ the best choice, how do you get the RINEX logs? There appears to be one in my home town. How straightforward is the post-processing, are there step by step guides?

I understand that the Reach takes points in WGS84, how easy is it to convert to OSGB1936? Especially for vertical Z height to convert to m OD? Is this possible in realtime? For post-processing from WGS to OSGB, are there simple step by step guides?

All help appreciated! Thank you.

[jurijs.jeshkins]

Hi!

I’d mostly be surveying excavation trenches and structures. Spot heights, extents, baselines etc. How easy is it to set up codes for types of point?

You can use namecoding, such as B for baseline, H for height etc. For now, it is the only option with the standalone software from Reach. Or, you can use Reach as your GPS, but for mapping use some other software, like Mobile Mapper.

What would be the options for getting towards centimetre accuray? Base station will generally be no more than 100m from Rover.

PPK is the answer to your question. If you have a local NTRIP caster station nearby, you can get RINEX out of it and process your base station against it. Then, try to process your rover against base station. This is usually how I am dealing in such occasions.

how do you get the RINEX logs? There appears to be one in my home town. How straightforward is the post-processing, are there step by step guides?

You should check your NTRIP caster. In my country we have RINEX for free. I don’t know, how is it in UK. Post-processing is quite straightforward. There is a guide from Emlid - https://docs.emlid.com/reach/common/tutorials/gps-post-processing/ . Start from here.

I understand that the Reach takes points in WGS84, how easy is it to convert to OSGB1936? Especially for vertical Z height to convert to m OD? Is this possible in realtime? For post-processing from WGS to OSGB, are there simple step by step guides?

For now with Emlid software it is not possible to convert coordinates in realtime. I would recommend to do everything in WGS84 and then convert all the points to OSGB1936 in some GIS software. QGIS is a wonderful free project you should try. There are plenty of tutorials on how to convert points form one system to another. Height conversions can be tricky.

[chiz]

Many thanks, that is really useful information.

The coding options sound ok for the first few jobs -there’s a lot to get to know and I think a simple set of codes and a good survey notebook would let me get on with learning the other aspects of the instrument. Does each namecode have an incremental number eg B1, B2, B3?

I will look into the NTRIP and RINEX, hopefully someone in UK can help! Is NTRIP/RINEX free in UK?Would I need mobile internet connection to use NTRIP? Would NTRIP be ‘live’ so I could use it for stake-out as well as surveying?

I use QGIS already, so that is not a problem, I could use a dumpy level for z coords until I have the conversion nailed.
Many thanks for your help

[andrew.yushkevich]

Hi @chiz,

Does each namecode have an incremental number eg B1, B2, B3?

You can use any code that suits you. The default point name is “Point1”, “Point2” etc.

I will look into the NTRIP and RINEX, hopefully someone in UK can help! Is NTRIP/RINEX free in UK?Would I need mobile internet connection to use NTRIP? Would NTRIP be ‘live’ so I could use it for stake-out as well as surveying?

Hope someone will provide you with detailed info about NTRIP in the UK.

As for the real-time Internet connection, there’re 2 ways to work with NTRIP: RTK and PPK.
I’d recommend you to read more about it here (RTK, PPK).

PPK is the answer to your question. If you have a local NTRIP caster station nearby, you can get RINEX out of it and process your base station against it. Then, try to process your rover against base station. This is usually how I am dealing in such occasions.

If you’re limited in Internet connection, you can use the workflow @jurijs.jeshkins described.
Otherwise, it’s much easier to connect Reach to the Internet and start getting corrections in real-time.

[chiz]

Many thanks Andrew, I have read the notes on the EMLID page, I’m just hoping a UK user can help with local details!