GPR surface & bed picking – participant instructions

ℹ️What this is

Thank you for taking part! We are measuring how consistently experts pick reflections in glacier GPR radargrams. On each image you draw two lines: the glacier surface and the bed. There are no graded "right" answers – we want your natural interpretation, so please pick as you normally would.

📖 Please read the instructions below carefully before you start picking.

Start picking → Upload your results

Start opens the picking tool. You will be asked for your name/initials only when you download your results (used in the file name). Upload opens the results form in a new tab.

✏️How to pick

Choose the horizon with the Surface (s) / Bed (b) buttons (or the s / b keys). Surface draws in cyan, bed in orange.
Surface: left-click along the top reflection of the ice body.

⚠ Note – snow cover: some radargrams were recorded with a thin layer of winter snow on top of the glacier. On those images the uppermost reflection is the air–snow surface, and a second, slightly deeper reflection marks the snow–ice interface (the true top of the ice). Please pick the surface along the snow–ice interface – the top of the ice – not the air–snow surface, so that the snow layer is excluded from the ice thickness.

Bed: left-click along the ice–bedrock reflection – the bottom of the ice. Where the ice lies above an air-filled cavity, follow the bottom of the ice (the ice–air interface inside the cavity), not the rock below.
Add points left to right. To move a point, drag it to a new position (grab it with the left mouse button); the line always reconnects left to right. Zoom with the mouse wheel, pan by dragging with the right mouse button. "Undo point" (Ctrl/Cmd+Z) and "Clear horizon" act on the horizon you are currently picking.
If you cannot interpret the bed on an image, tick "bed not interpretable" (you can still pick the surface) and move on – please do not guess.
Move between images with Next / Prev (or the arrow keys); your lines are kept. The counter in the top-left corner shows which radargram you are on (e.g. "Radargram 3 / 15") so you can see how many remain.

Note – image quality varies: all radargrams were processed together in a single batch with identical settings, so some look clear while others are noisier. The surveys used center frequencies of 75–150 MHz, with expected ice thicknesses of up to about 100 m. Please pick as best you can. If a radargram looks particularly poor or hard to interpret, a short comment about it (by email, see below) would be very welcome.

✅When you are finished

When you have picked the last radargram, a "thank you" message appears in the tool. Click Download my results (CSV) – this saves a file named analyst_YOURNAME.csv.
Upload that file using the green Upload results button (at the top of this page, or inside the picking tool). You will be asked to sign in to Google so the file is saved to our project drive.

🔎Please

Work independently – do not discuss or compare picks with other participants.
Pick both horizons on every image you can.
Try to finish in one sitting: your work is held in the browser tab and is saved only when you click Download. Nothing is sent anywhere until you upload.

Start picking →

Ready? This opens the picking tool. You can return to these instructions anytime via the "? Instructions" button in the tool.

🙏Thank you

Your time and expertise are greatly appreciated – these picks directly support the evaluation of UAV-borne GPR ice-thickness measurements in the MELT.AI project. If you have any questions about the task or run into technical problems, please get in touch:

Anna Siebenbrunner
GEORESEARCH & Technical University of Munich
anna.siebenbrunner@georesearch.ac.at