Last updated 4Oct22


In September 2022, surveyor friend Mike Lavis encouraged me to have a look at ACTMapi. Two areas are of interest.

Survey Marks

Empirical observations from social media point to the fact that trig bagging is a very popular pastime. It provides another reason to ‘get out and breathe a bit of fresh air’ and good views from vantage points. I’ve had my turn at ACT trig bagging, but am not as keen as some.

ACTmapi provides access to locations in both grid (UTM/GR) and geographical (lat/lon in decimal degrees) coordinates for ACT survey marks.

  1. Go to ACTmapi at

    ACTmapi landing page

  2. Activate the ‘New GDA2020 Survey Infrastructure’ tile

    ‘New GDA2020 Survey Infrastructure’

  3. (OK through any layers not loading messages if the layers are not relevant – I understand there can be server capacity issues)
  4. Activate the Layers link bottom left. Ensure you have Survey Control Marks GDA 2020 and Survey Control Marks ACT GRID ticked

    Appropriate layers and zoom to area of interest

  5. Pan and zoom to an area of interest
  6. Activate (click on) a survey mark. Activate the View Additional Details link. Scroll down the survey mark Description panel on the left. You’ll see details about the mark, including location in UTM and lat/lon in decimal degree format. Or activate the Panel Actions Menu icon to the right of the survey mark name and activate Show Expanded View.

    Survey mark detailed information

  7. Pop that in your navigation device and go bag a trig!

As an example, I regularly walk up to Tuggeranong Hill with its TG84 quadruped trig. ACTmapi shows me there is a nearby survey mark TG83. ACTmapi shows its location as UTM 55 691144.215 6074778.081 (MGA2020) and lat/lon -35.27076418S 149.062227728E (GDA2020). I don’t need the location down to the millimetre and, for my purposes, the datum GDA2020 is close enough to WGS84. So I pop the location GR 9114 7477 in my GPSr and away I go. I wonder what’s there? I could find nothing on the morning of 4 Oct 22. Similarly with TG4 on the afternoon of 4 Oct 22. A few flat areas about where a bolt could be underground, but I don’t want to dig the place up like a pig.

Items of Historical Interest

On 25 Sep 22 we found a survey peg on the flanks of Mt Majura and revisited the stone boundary wall and post and rail fence. Mike did some excellent survey sleuthing to determine their uses.

  1. Go to ACTmapi at and activate the ‘Historic Plans’ tile
  2. Activate the Layer link and choose appropriate layers (eg. Parish Maps Index, Canberra Parish and Pialligo Parish)
  3. Activate the Advanced Tools tab
  4. Activate the Upload Data icon and Add Data to Map (eg. a gpx file)

    gpx file uploaded onto Parish maps

  5. Here’s the gpx file on a 1:25000 topographic map that was uploaded

    Mt Majura and Justice Robert Hope Park NRs

  6. Next, export the map from ACTmapi. Use the Export icon, save in TIFF format with Include Georeference Data. Do View Image to download it.
  7. Calibrate the map tif in OziExplorer using known waypoint locations.
  8. Create waypoints in OziExplorer at points of interest to investigate

    Map calibrated in OziEplorer and ready to use

  9. The map exported from ACTmapi could probably be set up in Google Earth. Need to check this out.