Version 3 (modified by emca, 8 years ago) (diff)

--

Leica IPAS TC navigation processing

IPAS TC combines the IPAS Pro and Graftnav into one process.

All files should be named according to the year, julian day and flight letter (where applicable) - YYYYJJJf.*

Setting up the Project

  1. Open IPAS TC
    1. Select new, navigate to the ipas folder of the relevant project, and give your project a name as above and click create
    2. This will create a *.itp file which will store all the parameters used
    3. This brings you to the Project Overview dialog box
  2. Select Aircraft Data File
    1. The Data File should point to ipas/raw/*.000 file
    2. The Extract Directory should be created automatically as ipas/extract, if not create it
    3. Click Extract Raw data. When that has finished, check the messages for any errors and click accept
  3. This will automatically bring you to the GNSS Base Station dialog box
    1. Under Options for GNSS select User Differential GNSS (for PPP see below)
    2. From here you can select Add Base Station or Download Service Data
    3. Up to 8 base stations can be added
    4. To add a base station select the appropriate Raw Data Folder on the Raw GNSS File tab and click convert.
    5. Check the correct Co-ordinate and Antenna information have been added and accept
    6. When you have finished adding any additional base stations select accept
  4. The final stage before processing is to set the Configuration
    1. Click on configuration
    2. Enter the lever arm values under the GNSS and IMU tab
    3. On the GNSS tab select Processing Options (small button on the far right). Use the following settings:
      1. Use GLONASS if present should be ticked
      2. Should use L2 Carrier. Disable this if the base station is less than 10km away
      3. Select Engage Only
      4. Quality Acceptance - Q2 (99%)
      5. Click OK, then accept to go back to the main Project Overview
  5. Select Start Processing
    1. This will process the forwards and backwards solution, smooth the data and output the *.sol file

Note: If you get an error saying "Cannot load MANUFACT.dtm" copy the following folder C:\Documents and Settings\Default User\Application Data\NovAtel\IPAS_TC_3_00 to your own user space C:\Documents and Settings\$user\Application Data\NovAtel\

Analysing the Data

  1. Select Launch Graphical Analysis Window
    1. Initially you will see the trajectory of the aircraft, coloured by GPS time
    2. Click on Show Toolbox
    3. Select Solution Analysis and choose which parameters you want to plot.
      1. Check the Position Separation -this should ideally be less than 0.05m.
      2. The ambiguity fix is shown on the same plot, for a fixed solution this will be 2.
      3. Check the Position Accuracy - this should ideally be less than 0.035m in lat/long and 0.05m in height
    4. If you do not get an acceptable solution, try to change some of the settings and rerun the processing
      1. Select Windows > Project Overview > Configuration.
      2. On the GNSS tab, select GNSS processing options.

If you still cannot get a good solution, you can try processing using the old IPAS Pro.

Additonal Notes:

The accuracy using IPAS TC is approximately the same as using IPAS Pro and GraftNav combined IPAS TC can operate with fewer satellites and deeper turns => more reliable observations

Leica don't recommend using recomputing the base station position as this introduces more unknown parameters into the mix.

When you process the navigation it also produces the sol file, you cannot process them separately. If you wish to compare two sol files, remember to change the output name of the sol file.

Estimate Lever Arms

In general you don't need to select this. However, it can be used to check the accuracy of the lever arm values.
If you have good data (3 mins flight alignment, figure of 8, good satellite data) and the lever arms values are significantly off then consider remeasuring.

When Using Download Service data

If you can't get a fixed solution or fixed ambiguity check the base station settings.
Some satellites need a correction file to offset to older satellites (not applicable to the Leica stations)

PPP Mode

  • Select use Precise Point Processing from the Setup NSS Base Station window.
  • Click on Check Availability to see what data are available.
  • This will display all precise data that has been found, and will be default select the final orbit.
  • Do not use 'Final clock (30s)' - better to use 5 or 1 second data.

PPP mode is not recommended for project under 90 minutes.
It is not possible to estimate the lever arm in PPP mode.

Can process the base station data in PPP mode to get a fix on the co-ordinates.

Lever arms (March 2011)

Lever arm values to enter into the software for 2011 onwards are:

X Y Z
GNSS -0.144 -0.029 -1.672
IMU -0.411 0.206 -0.192
User Frame -0.142 -0.001 -0.188

These values are entered in the flight planning software and should automatically populate in IPAS.
The GNSS and IMU values can be changed in IPAS TC if they are incorrect. The user frame values cannot. They can be checked in ipas/extract/*extract.log. If you find these values are not correct let Ops know so they can change them to what they should be.