> For the complete documentation index, see [llms.txt](https://horus-make-sense.gitbook.io/documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://horus-make-sense.gitbook.io/documentation/systems/citymapper/data-processing/pospac-mms.md).
# POSPac MMS
Processing the log to centimeter level accuracy
This page described how to post-process positional data from an Applanix GNSS/IMU system.
Post-Processing is required to improve the accuracy of the images their positions.\
The raw positions recorded by the Applanix may be anywhere between 50cm - 4m, by processing the log data in POSPac this can be improved to single-digit centimeter level.
{% hint style="info" %}
If your system has RTK and/or RTX you may not need to post-process, see [this chapter](/documentation/tutorials/working-with-horus-recordings/quality-checks/gnss-accuracy-and-trajectory.md) on how to verify if this process is required.
{% endhint %}
## 1. Prerequisites
To proceed with the post-processing process, the following prerequisites must be met:
* POSPac MMS with an active license
* Your Applanix Log file
## 2. Correcting the Trajectory
1. Start POSPac MMS
2. Click **New Default Project** in the **Project** tab.\
3. Import the log file from LV POSView.\
This can be done via the following methods:\
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• Click on the Log file and drag-and-drop it onto the grid in POSPac MMS.\
• clicking **Import** in the **Project** tab (a sidebar pops up), click **...** and select the folder containing the POS data file, then select the POS data file in the listing and click on the **Import** button.
4. The import process may take a while.\
Various data will also be downloaded, this does not require user-intervention.\
\
When the import process is finished a trajectory will appear on the grid, indicating the the import is done.\
\ \
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A dialog may appear titled **Rover Antenna Specification.**\
Depending on your system select the appropriate antenna type.\
• Citymapper - **LV59**\
• Vertex - **AV28 w/Ground Plane**\
Click on **OK** to Continue\
\
When the data is imported a trajectory will appear on the grid.
5. Click **Project Settings** in the **Project** tab.
1. Navigate to **GNSS-Intertial Processor -> Lever Arms and Mounting Angles.**
1. Set the **Standard Deviation** to **<3cm.**
2. Navigate to **Export -> Settings.**
1. Set **Output Format** to **Horus Export Format....**
2. Set **Output Rate** to **Event 1 Time.**
3. Set the **Coordinate System** of the **Mapping Frame**.\
Uncheck the **Default Mapping** Box, click **Mapping Frame**, set the **Datum** to the coordinate system that is used in your region or is required. Click OK to save the changes. \
\
When in doubt on which coordinate system to use, check with Horus support or your end-customer.
4. Set the **Height.**\
By default the **Ellipsoid** model is used to determine height.\
In some instances, you may want to switch to an **Orthometric** model.
3. Click **OK** to save and close the **Project Settings** window.
6. Import **Base Station** data.\
A GNSS base station is a **stationary receiver** set up with a precisely known location that collects satellite signals to calculate errors in GNSS data. By knowing these errors, POSPac can correct these errors from the Applanix log, reducing the error to centimeter-level.\
\
There are multiple methods of introducing Base Stations into POSPac. Choosing the correct method is based on the trajectory of the Applanix log.
{% tabs %}
{% tab title="Single Base Station" %}
Single Base Stations work best when they are within 50km of any point of the trajectory.\
Due to importing only a single station this is quicker than the multi base station options without losing any accuracy.\
\
To import a single base station you can use the build-in **Find Base Stations** function or import **Rinex** data from an external source.\
\
**Find Base Stations**
1. Select the ‘**Find Base Stations**’ button under the ‘**Projects**’ tab.
2. Open the ‘**SmartSelect**’ menu and click on ‘**SingleBase**’.
3. Wait for the process to finish, this might take some time.\
When finished, an icon will appear on the grid with a flag.
**Importing External Base Stations**\
Get Rinex data from an external source, ensure that its position is within 50km for best results and that the duration overlaps the Applanix log data.
1. Drag the Rinex files onto the grid to import the data. When imported a green dot with the base station name will appear on the grid.
2. Set the **coordinate system** of the Base Station.\
Right click on the base station and select: ‘**Coordinate Manager**’. Open the ‘**Frame**’ tab and for the ‘**frame**’ setting specify the coordinate system to match the system of the Base station data.\
(Check with the data provider what the correct coordinate system is)
3. Set the Rinex data as a Base Station.\
Right click on the base station and select ‘**Set Base Station**’\
The icon should now be marked with a flag.
When processing (see step 7), set the **GNSS Mode** to **In-Fusion+ Single Base**.
{% endtab %}
{% tab title="Smartbase" %}
A Smartbase solution is a virtual reference station generated by multiple surrounding base stations. The benefit of a smartbase station is when the radius of your trajectory is larger than 50km.\
\
**Importing a Smartbase solution**
1. Select the ‘**Find Base Stations**’ button under the ‘**Projects**’ tab.
2. Open the ‘**SmartSelect**’ menu and click on ‘**SmartBase**’.
3. Wait for the process to finish, this might take a while time.\
When finished, multiple stations will be placed surrounding the trajectory.
4. Click on '**SmartBase Quality Check**' and wait for the initial check to complete.\
A window with a summary of the check will appear, click on **Continue** until the SmartBase solution is created indicated by the yellow smartbase region.
5. When processing, select **In-Fusion Smartbase** as the **GNSS Mode** ( see step 7)
{% endtab %}
{% tab title="MultiSingleBase" %}
A MultiSingleBase solution is used when you have very long sightlines, requiring multiple base stations to cover the trajectory.\
This uses stations placed alongside long stretches of the trajectory, whilst a SmartBase uses stations to create a circle around the trajectory.
**Setting up a MultiSingleBase solution**
1. Import multiple base stations along the route, with an interval of no more than 50km.\
See the Single Base Station tab on instructions on how to import the base stations
2. In the **Project Explorer** on the left, select all the base stations.
3. Under the **Project** tab, click on **Create MultiSingleBase+ Station**
4. When completed, a new point will be added to the grid, indicating the new MultiSingleBase station.
5. When processing (see step 7), set the **GNSS Mode** to **In-Fusion+ Single Base**.
{% endtab %}
{% endtabs %}
**\*Note** If you have a PP-RTX license then this step may be skipped, as this is set via the GNSS mode in the next step.\
If your recording system has RTK and/or RTX, then first [check the quality](/documentation/tutorials/working-with-horus-recordings/quality-checks/gnss-accuracy-and-trajectory.md). By processing with POSPac you can usually improve the solution slightly and remove some of the deviations, but if the error is low enough, you may be able to skip processing with POSPac.
7. **GNSS-Inertial-Processor -** Configure\
Open the **GNSS-Inertial-Processor** under the **Project** tab. \
\
Verify that the settings are configured correctly.\
**GNSS Mode -** Set the mode to align with the method chosen in the previous step.\
**Heading Sensor** - Should be set to *GAMS*\
DMI - Should be *Disabled* unless your recording vehicle has a DMI sensor connected.
8. **GNSS-Inertial-Processor -** Process\
To start processing the data, click on the *Run* button at the bottom of the panel.\
\
Wait for the processing to complete, this may take a while.\
Once done, a green line will appear, indicating the corrected trajectory.
9. Verify the accuracy of the processed data.\
Please see the [GNSS Accuracy & Trajectory](/documentation/tutorials/working-with-horus-recordings/quality-checks/gnss-accuracy-and-trajectory.md) page on how to check the accuracy in POSPac.\
Check the position error of the *Smoothed Performance Metrics, Reference Frame* option.\
\
After processing an average of <5cm is expected with some outliers being normal.
10. Exporting the Corrected Data.\
If you are happy with the result, then the data can be exported.\
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\- Go to *Tools -> Export*.\
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\- Click on the right button for the **Export File Name** and define the export location and name\
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\- Verify that the following settings are configured to the following:\
**Export File Format -** Horus Export Format\
**Output Rate** - Event 1 Time\
**Output Height -** Should be the same as set in step 5.b.iv.\
The rest should be left to their default settings.\
\
At the bottom, click on the *Export* button to write the data to the disk.
You have now processed the raw data log from the Applanix into centimeter level accurate data.\
The next step it to update the recordings with the corrected position with the Horus Position Fixer.
\
\
A dialog may appear titled **Rover Antenna Specification.**\
Depending on your system select the appropriate antenna type.\
• Citymapper - **LV59**\
• Vertex - **AV28 w/Ground Plane**\
Click on **OK** to Continue\
\
When the data is imported a trajectory will appear on the grid.
5. Click **Project Settings** in the **Project** tab.
1. Navigate to **GNSS-Intertial Processor -> Lever Arms and Mounting Angles.**
1. Set the **Standard Deviation** to **<3cm.**
2. Navigate to **Export -> Settings.**
1. Set **Output Format** to **Horus Export Format....**
2. Set **Output Rate** to **Event 1 Time.**
3. Set the **Coordinate System** of the **Mapping Frame**.\
Uncheck the **Default Mapping** Box, click **Mapping Frame**, set the **Datum** to the coordinate system that is used in your region or is required. Click OK to save the changes. \
\
When in doubt on which coordinate system to use, check with Horus support or your end-customer.
4. Set the **Height.**\
By default the **Ellipsoid** model is used to determine height.\
In some instances, you may want to switch to an **Orthometric** model.
3. Click **OK** to save and close the **Project Settings** window.
