Read the LiDAR drainage layers

A prepared field has three drainage layers. Together they answer the questions you ask before you cut a ditch: where does the water go, where does it sit, and which low spots fill first.

They show on the LiDAR & Mapping map right after Prepare Field. You can add them to any survey or grade map from My LiDAR Fields (Open My LiDAR Fields).

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Flow Routes: where the water goes

Black lines follow the path water takes downhill across the LiDAR surface.

• Thicker line, more water. The width grows with the ground that drains into that line, from thin (under 2 acres) to the thickest (100 acres and up).
• Lines that drain less than about a quarter acre are left off.
• Lines stop at the field boundary you drew.
• Lines draw a little lighter when the ponding layer is on, so both stay readable.

Flow lines have no opacity slider; switch them on or off.

Ponding Risk: where water sits first

Ponding ranks every spot in the field by how early it gets wet after rain, from Wet last to Wet first. Colour follows the rank:

• Red and orange: wet first. Water collects here before anywhere else.
• Yellow: wets early.
• Green, teal and light blue: wets later. Hidden at the default cutoff.

The ponding cutoff

The cutoff hides everything ranked below it. It runs from 0 (Wet last, left) to 100 (Wet first, right) and starts at 75, which shows the yellow-to-red spots.

• Slide right to see only the worst spots.
• Slide left to see how far the wet ground spreads.

The row reads Ponding cutoff 75. It is a rank, not a depth. Each field has its own cutoff; it goes back to 75 when the app restarts.

Depressions: the low spots

Depressions are hollows with no way out on the LiDAR surface: water that gets in can only leave by soaking in, evaporating or overflowing. Shades of blue show how deep they are:

A hollow counts only if its deepest point reaches 6 in and it covers at least 100 m² (about 1,100 sq ft). Parts shallower than 3 in are not drawn. After Prepare Field, depressions are in the layer list switched off: turn them on when you want them. Ponding draws over them, so switch ponding off to see the hollows clearly.

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Change opacity and the cutoff

1. Tap the layers button

   The dark square button with a blue stacked-sheets icon, at the bottom right of the map. A window called Map Layers opens.

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2. Tap the small arrow at the left end of the Ponding Risk row

   LiDAR rows are under OVERLAYS. They carry an LDR badge and read like Section 12 West - Ponding Risk. Rows with sliders have a small arrow at their left end.

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3. Drag a slider

   The row opens. Ponding has an Opacity slider (starts at 100 %) and a Ponding cutoff slider. Depressions have an Opacity slider only (starts at 80 %). Flow Routes and Boundary have no arrow, only the switch.

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   Put your finger on a slider's round handle and slide it. The map behind the window updates as you move it.

   • Opacity, to the left: the imagery and your breadcrumbs show through the colour.
   • Ponding cutoff, to the left (toward Wet last): more of the field shows, down into ground that wets later.
   • Ponding cutoff, to the right (toward Wet first): only the worst spots stay.

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4. Tap Close

   At the bottom right of the window. The new settings stay on the map until the app closes.

The same sliders appear in My LiDAR Fields under each layer you tick there.

Use the layers to plan a ditch route

1. Start at the wet spots

   Turn on ponding and depressions. The red patches and dark-blue hollows are the ground you are trying to drain.

2. Follow the flow lines out

   From each wet spot, follow the black line downhill to where it leaves the field. That exit is your outlet candidate. The thick lines are where the most water already wants to go.

3. Thin it down to the lines worth cutting

   Open the Drainage Planner and raise the minimum drainage area until only the main paths are left. Save it as a plan so it loads on the grade map in one tap.

4. Check the ground

   Use the LiDAR elevation check to compare a low spot with the outlet. Look at the field for what the LiDAR can't know: culverts, tile, ditches cleaned or filled since it was flown.

5. Survey the route with RTK

   Drive the planned line with the drainage layers under your survey map. The design comes from your RTK survey, not from the LiDAR. See Survey a route.

What the layers can't tell you

• The age of the LiDAR. It shows the ground on the day it was flown.
• Pipes and culverts. LiDAR sees the road surface, not the culvert under it, so water can look trapped behind a road or field approach.
• Small features. At 2–5 m per pixel, a narrow field ditch or a dead furrow may not show.
• Grade for the blade. The layers are for planning. Survey and grade with RTK Fixed.