How to retrive base marker values from logs

Emlid Flow & Emlid Flow 360 Survey tools
1

Before creating a new thread, please refer to Emlid Flow docs or Support tips category of this forum.

In case you are creating a thread about an issue, it is necessary to provide the following information to get help:

  1. Emlid Flow app version.
  2. Detailed issue description. How does observed behavior differ from the expected one?
  3. Your step-by-step actions

Hi there,

App version: 8.11.

Issue: I managed to have a base markers value calculated over a period of 15 mins, while connecting to CORS (i.e. fix signal). However, I didn’t take a screen shot of the values (base marker’s values) and immediately proceeded to logging.

I am wondering is there a way to retrieve the base marker’s value from the log itself (I.e. raw Rinex with base correction, & position track) ? That base marker is suppose to act as my base for a LiDAR mapping project but I found out that each log’s Rinex header position keeps changing ( I recorded a multiple logs with the same static base).

Anyway, appreciate if anyone could show me a way/process to retrieve my averages base marker value from the recorded log.

Tq

3

Hi @pixventuresplt.dji,

Welcome to our forum!

If those coordinates weren’t recorded anywhere, it’s hardly possible to retrieve them. The RINEX header contains only the approximate marker position which was not corrected.

However, If you have the log from CORS, you can process it together with the RINEX from your receiver to get the fixed coordinates of the position.

Or you can also process RINEX from Reach in the PPP service to obtain the coordinate. But the file should match the requirements of the service to calculate the position.

Here are the guides that might be of great help:

2 Likes
4

I have been looking into the .llh file and it seems to contain the base coordinates. Wondering if you guys have explored the .llh file and be able to extract the averaged values. i asked chatGPT and this is what i got. Would you be able to confirm this would indeed work?

Thank you for providing more information. Based on the website you mentioned, it appears that .llh files are associated with RTKLIB, a software package used for real-time kinematic (RTK) positioning. These files might contain latitude, longitude, and height data for GPS or GNSS positions.

To calculate average values from a .llh file using RTKLIB, you can follow these general steps:

  1. Download and Install RTKLIB: If you haven’t already, download and install RTKLIB from the official website (www.rtklib.com).
  2. Open RTKCONV: RTKCONV is a utility in RTKLIB that can convert various GPS/GNSS log file formats, including .llh, into more common formats like RINEX.
  3. Convert .llh to RINEX: Use RTKCONV to convert the .llh file to RINEX format. RINEX is a standard format for GPS/GNSS data and is more widely supported. This conversion will make it easier to work with the data.
  4. Process RINEX Data: Once you have the data in RINEX format, you can use RTKLIB’s other utilities like RTKPOST or RTKNAVI for post-processing and analysis. These utilities provide options to calculate various metrics including average positions.
  5. Calculate Average Coordinates: Depending on your specific needs, you can calculate average latitude, longitude, and height values using the processed data. RTKLIB utilities like RTKPLOT might have features that allow you to visualize the data and compute statistics.
  6. Export Results: After calculating the average values, you can typically export the results to a file or copy them to a clipboard for further use.

Remember that the exact steps and options may vary based on the version of RTKLIB you are using and the specific capabilities of its utilities. Make sure to refer to the official RTKLIB documentation and user guides for detailed instructions and examples related to your version of the software.

Additionally, keep in mind that GNSS data processing can be complex and requires a good understanding of the data and the software. If you’re new to this, it might be helpful to consult resources like user guides, tutorials, and forums related to RTKLIB and GNSS data processing.

5

Basically, it suggests using the post-processing tools to retrieve the position. But this information isn’t quite correct. It’s not possible to convert the .llh file to RINEX since they contain completely different data.

The .llh file has the latitude, longitude in degrees, and height in meters of a position. The height here is the ellipsoidal height to the antenna phase center. To figure out the position on the ground, you need to subtract the height of the pole the receiver was placed on including the antenna offset. But It’s very easy to confuse something with this method which can lead to incorrect results. I still recommend getting the position of the receiver using the ways I described above.

1 Like
7

Full disclosure–I typically use my Emlid device as a NMEA GNSS device with Survce and expectations made of this software should not directly apply to Emlid’s Flow.

Many data software collector softwares have the ability to export out their raw data in different formats with RW5 being a common format. Survce has the ability to export out your base location if you use their approved hardware (ie. BRX7, etc.). I have included an example below. Note that the “#words words words” are comments that I have added for additional clarity in this post.

#job number and date
JB,NM20230814BRX7 - JLJ(230067),DT08-14-2023,TM19:17:17

#the data collector takes the scale as given from the RTN; we used CANNET for this example
–MO,AD0,UN1,SF1.00000000,EC0,EO0.0,AU0
–SurvPC Version 6.16
–CRD: Alphanumeric

#coordinate system/project along with hardware info
–Projection: CANADA/NAD83/UTM zone 17N
–Equipment: Carlson, BRx7
–Antenna Type: [BRX7 Internal],RA0.0785m,SHMP0.0547m,L10.0701m,L20.0629m,–L1/L2/L5 Internal Antenna
–Localization File: None
–Geoid Separation File: C:\Carlson Projects\Data\Geoids\Canadian_ht2_0.gsb N41°01’00.0" W141°58’59.0" N83°58’58.0" W048°01’03.0"
–Grid Adjustment File: None
–GPS Scale: 1.00000000
–Scale Point not used
–Entered Rover HR: 1.7900 m, Vertical
LS,HR1.8601

#I logged RINEX on the rover so I can PPK if necessary off one of the network bases
–GPS Log File: 230814ROV1230067.bin rover open Carlson,BRx7
–GNSSLOGRCVR,FL230814ROV1230067.bin,SRROVER,RND2041500803050,RMHEMBRx7,RF6.0Aa04a,1.19,0.66.220415A
–GNSSLOGANT,FL230814ROV1230067.bin,AN,AMHEMS631 NONE,LI1000,AG1.790,PA0.070

#this is the setting we have to use to make CANNET work with non-Trimble equipment
–RTK Method: RTCM V3.2, Device: Data Collector Internet, Network: NTRIP caneastvrscmrx

#this is the important bit for you; one can take this info and convert it to find your base point; you could use something like SGSS Tools->Coordinate Converter to do so ( Coordinate Calculator | Simple Geospatial Solutions )
BP,PN1234_BASE_1,LA42.544145257737,LN-81.174052470818,EL224.2120,AG0.0000,PA0.0000,ATAPC,SRROVER,–
–DT08-14-2023
–TM19:17:44
–Entered Base HR: 0.0000 m, Vertical
LS,HR0.0000

#CANNET uses a VRS so I always record it just to know where it is; it changes often which is one of the annoyances of VRS; it doesn’t have a “locked” base station like a standard RTN or one putting out iMAX/MAX solutions
GPS,PN1234,LA42.544145257737,LN-81.174052470818,EL224.212006,–CANNET RTN VRS RTK BASE
–GS,PN1234,N 4751030.8092,E 475954.0038,EL259.6099,–CANNET RTN VRS RTK BASE
–Entered Rover HR: 1.7900 m, Vertical
LS,HR1.8601

#here we get to work and start taking shots
GPS,PN6000,LA42.544003779713,LN-81.173942781220,EL227.579673,–CC CUTTEE SDW
–GS,PN6000,N 4750987.0815,E 475978.7219,EL261.1179,–CC CUTTEE SDW
G0,2023/08/14 23:27:04,(Average) - Base ID read at rover: 1234
G1,BP1234_BASE_1,PN6000,DX29.46753,DY-28.05602,DZ-29.68381
G2,VX0.00001270,VY0.00006234,VZ0.00004335
G3,XY-0.00000129,XZ-0.00000160,YZ-0.00002951
–GT,PN6000,SW2275,ST170832800,EW2275,ET170843800
–Valid Readings: 11 of 11
–Fixed Readings: 11 of 11
–Nor Min: 4750987.0775 Max: 4750987.0840
–Eas Min: 475978.7206 Max: 475978.7230
–Elv Min: 261.1153 Max: 261.1215
–Nor Avg: 4750987.0815 SD: 0.0020
–Eas Avg: 475978.7219 SD: 0.0007
–Elv Avg: 261.1179 SD: 0.0019
–HRMS Avg: 0.0060 SD: 0.0002 Min: 0.0057 Max: 0.0065
–VRMS Avg: 0.0090 SD: 0.0004 Min: 0.0085 Max: 0.0098
–HDOP Avg: 0.5615 Min: 0.5615 Max: 0.5615
–VDOP Avg: 0.9765 Min: 0.9764 Max: 0.9767
–PDOP Avg: 1.1265 Min: 1.1263 Max: 1.1266
–AGE Avg: 1.0000 Min: 1.0000 Max: 1.0000
–Number of Satellites Avg: 28 Min: 28 Max: 29
–DT08-14-2023
–TM19:27:10
–Calculated GPS Scale: 0.99957168

We later use the data collector to scale things to ground on the fly as we are doing a “flatlander” cadastral survey.

If Flow has a format export option, it might be worth seeing if it has the info in an RW5 export. I don’t know as we also use total stations with most of our work and Flow does not have an option to use that hardware.

To be completely fair, one should not expect that of Emlid, but it makes it so that we use their products with data collection software that does support total stations. I would totally switch if they did as I really enjoy all of Emlid’s products.