Click Build Elevation Map, draw a polygon around your area of interest, and double-click to finish. In seconds, you’ll see a colorized LiDAR-based HD elevation overlay with 3D hillshading.

The overlay’s resolution adapts to selection size:

- Small areas (under a quarter-section) render at ~1 m/pixel or finer in most areas.

- Large regions (state-sized) render at ~100 m/pixel or more.

In Canada, HD overlays require LiDAR coverage (in the US it should work everywhere). If you encounter a 500 error, the server is likely busy or under maintenance—wait a few minutes and retry. Evening or weekend disruptions usually clear within an hour or by the next morning.

To download the raw DEM you’re viewing, click Save LiDAR WGS84 under File/Project. This exports a GeoTIFF in EPSG:4326 (WGS84) with elevation in meters.

For non-LiDAR areas or custom data, import your own GeoTIFF using GeoTIFF → Elevation Map (GeoTIFF must be using EPSG:4326 WGS84 coordinate system with elevation in meters) to build the HD overlay. See our video tutorial for formatting guidance.

Click Create Drainage Layers, then draw around your area of interest just as you would when generating an HD elevation map. Geo-Surface will download LiDAR at a similar resolution (higher resolution for smaller areas), upload it through your browser to a cloud-based GIS server for processing, and automatically download the resulting flow, depression, slope, and wetness layers back into your session.

Once the Drainage Layers are generated, you can download the raw LiDAR DEM in a projected CRS (EPSG:3857 Web Mercator) using the Save LiDAR EPSG:3857 button under File/Project.

Because the processing server requires projected DEM files (such as 3857), the system works in projected coordinates for analysis. However, for easier mapping and compatibility, the resulting depression, slope, and wetness potential layers are converted back to WGS84 (EPSG:4326) when downloaded back into Geo-Surface, so when you export any of these layers they will be in WGS84 CRS.

You may also upload your own GeoTIFF to generate the same Drainage Layers using the GeoTIFF → Drainage Layers button. Your GeoTIFF must be under 6 MB in size and use a projected CRS like UTM Zone x or EPSG:3857.

The HD Flow layer is generated using TauDEM’s StreamNet output, which is then converted to KML for display in Geo-Surface and for download via Export Flow → KML.

For smaller areas like fields, you can adjust the minimum contributing area shown using the slider. At 0 acres, all flow lines will be visible—including very minor tributaries. As you slide to the right, smaller, less significant tributaries are filtered out, showing only larger flow paths.

On larger regions, most flowlines already exceed 25 acres of contributing area, so the slider may not have much visible effect.

The exported KML file includes all original StreamNet attributes, allowing you to further analyze the flow network in GIS software if needed.

Depression areas are computed by subtracting the elevation of a pit-filled (depressionless) DEM from the original raw elevation DEM. Wherever a depression was filled, the result is a negative value representing the depth of the depression in meters.

Geo-Surface converts these values to centimeters for easier visualization. To provide smoother and less spotty coverage, depression layers are resampled to 30 m pixels if the original DEM resolution is finer than 30 meters.

Using the slider, you can control which depressions are shown—starting from all depressions and progressively filtering out shallow areas up to >30 cm deep.

When you download the depressions layer, you’ll get the full depression depth data (>30 cm), ready for further analysis in any GIS software.

Geo-Surface automatically converts these values to centimeters for easier visualization. Using the slider, you can control which depressions are shown—starting from all depressions and filtering out shallow ones up to >30 cm deep.

When you download the depressions layer, you’ll get the full set of depression depths greater than 30 cm, which you can analyze further in any GIS software.

The Slope Mask layer is a simple pixel-based slope calculation, expressed in percent (%), derived directly from the raw DEM. For smaller areas of interest, the slope layer is resampled to 30 m pixels to smooth out small fluctuations and eliminate noise from minor elevation variations.

Keep in mind that raster-based slope and profile tool slope are calculated differently.

- Raster slope is based on elevation changes between each pixel and its immediate neighbors.

- Profile tool slope measures elevation change along a line between selected points, not based on neighboring pixels.

As a result, slope values you see in the raster layer may differ slightly from the slopes shown in elevation profiles along drawn routes.

The Wetness Potential layer is based on a classic Topographic Wetness Index (TWI), calculated using TauDEM outputs and resampled to 30m for smaller regions for smoothing. It combines local slope and flow accumulation derived from a depressionless DEM to highlight areas more prone to wetness or waterlogging—even if they are not formal depressions.

Since depressions are filled before wetness is computed, true depressions usually don’t show up in the Wetness Potential layer itself. To identify the wettest areas more completely, combine the Wetness Potential and Depressions layers. Depressions will flood first, followed by the low-lying areas that appear as you move the Wetness Potential slider from right (high threshold) to left (lower threshold).

Note that soil type and texture are not considered here, so wetness potential may be less accurate on lighter, sandier soils.

Use Draw Manual Survey to trace a proposed drain route directly on the map. An elevation profile of the underlying terrain will appear below the map as you draw. This can be done with or without first generating the HD Elevation layer, although without it, fetching elevation values from the LiDAR server may take a few seconds.

If you're in the field, you can also use your mobile device’s GPS to walk or drive a proposed route. Elevation values are still fetched from LiDAR (not from your device’s GPS altimeter), and the profile will appear the same way as if drawn manually.

To quickly check grades between points on the profile, simply click two or more points. A grade line will snap between them, showing the slope for each segment you select.

To trim the ends of any drawn profile lines, use Trim Laterals and draw a line that cuts through them to create two new line features. The shortest of the two will be automatically deleted.

Use Copy (Offset) Line to create an exact copy of the seleceted profile line, offset either left or right when standing at the outlet looking toward the inlet end. Up to 5 offsets can be created at a time. 

The Active Profile dropdown lets you select the line you want to work on. When you add grade lines, depth offsets, and other edits to a profile, its state is saved and recalled when reselected.

To add depth (e.g., simulating tile installation or deepening a surface drain), enter a value in Offset Depth, then click Apply Offset / Refresh. The red grade line will shift to the new depth.

Use Min Depth and Max Depth lines as visual guides. They don’t affect best-fit calculations, but show when your proposed grade goes deeper or shallower than your design targets. For tile designs, typical min/max values might be 24–60 inches for laterals, with mains often requiring deeper minimums.

Width is used to estimate earthworks for surface drainage—adjust it based on the desired ditch bottom width or implement width.

Min Grade is used for Best-Fit design. If the natural slope drops below the min grade, cuts will be made to maintain it. A minimum of 0.1% is typical for tile drainage; lower values are fine for surface drains.

To create a Best-Fit, click two points on the profile (usually outlet and inlet). Geo-Surface assumes the lower point is the outlet, but if needed, use Reverse Outlet to swap the start and end points.

Use Export 3D Line to export the active profile and assigned grade design for use in other applications.

The most important habit to maintain when using Geo-Surface is to regularly back up your design projects.
Because all your work is stored only inside your web browser (nothing is saved to external servers), the only way to protect your work against data loss is to create and save Backup files.

Best practice is to create a new backup after any major design changes.
Backup files are very small and will not take up meaningful space on your computer, but they can save you hours of work if something unexpected happens.

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📂 File and Project Controls Overview:

• Save Snapshot – Save a simple, high-quality image of the map for quick reference.

• Ditch Assist Image – Save a georeferenced JPG map and world file for use in Ditch Assist or other mapping software.

• Export Design → KML – Export your manually drawn and designed drain routes as a KML file for use in GIS or Google Earth.

• Import Design ← KML – Import previously saved design routes (KML format).
  (Note: KMLs only store lines, not full design settings. Always prefer backups for full project recovery.)

• Export Flow → KML – Export generated flow lines (from drainage analysis) as a KML file.

• Import Flow ← KML – Import a saved KML flow lines file into your current project.

• Backup Design Project – Save a full backup of your current project, including drawn lines, grade profiles, offsets, width, depth settings, and more.
  (Highly recommended before and after major updates.)

• Restore Design Project – Restore a previously saved backup file to instantly reload your work.

• Save LiDAR WGS84 – Download the raw HD elevation DEM as a GeoTIFF (EPSG:4326 WGS84, elevations in meters).

• Save LiDAR EPSG:3857 – Download the raw HD elevation DEM in a projected coordinate system (EPSG:3857, Web Mercator).

• Save Depressions – Download the mapped depressions raster as a GeoTIFF (EPSG:4326 WGS84).

• Save Slope % – Download the slope raster (% grade) as a GeoTIFF (EPSG:4326 WGS84).

• Save Wetness Pot. – Download the wetness potential raster as a GeoTIFF (EPSG:4326 WGS84).

With Geo-Surface Pro, your data is yours to keep.

Need the LiDAR you're viewing in QGIS or ArcGIS? Just one click and it’s downloaded to your hard drive. Export flow routes as KML files—ready for use in any GIS software or for easy viewing in Google Earth or Google Earth Pro. Want to import your depressions layer into QGIS? No problem, just save it to your hard drive! Likewise with the slope and wetness potential layers you generate. It's your data, you own it!

And we’re constantly expanding what you can generate and export, with new layers and features added regularly.