Elevation Process

landplan.io gives every part of a septic design an elevation as you draw it, so you can check gravity flow and size a pump before you visit the site. You then replace those elevations with what you measure on site.

Elevations as you draw

When you draw a tank, a pipe, a trench or a bed, landplan.io looks up the ground elevation where it sits. A sewer main, for example, gets the elevation at the point you start it and at the point you end it. These elevations go into Details > Elevations, where the inverts and the bottoms of the parts are worked out from them.

All the elevations of the design are in the elevation list.

Where the elevations come from

Each elevation comes from the best source that answers for the spot:

1. The DEM tiles processed for the site, from public lidar such as USGS 3DEP. Where a tile isn't processed yet, USGS 3DEP is read directly.
2. When that can't answer: the project DEM inside the parcel, then a web elevation service (USGS or Google), which is slower and coarser.

The source shows with the elevation: on the card of the Elevation tool and under the elevation in Site Benchmark (for example From USGS 3DEP 1 m), and on the chip of the elevation profile.

To see how the ground runs between two spots, draw a line with the elevation profile. It graphs the ground, the slope and the steepest stretch along the line, and downloads the samples as a CSV file.

A hierarchy of accuracy

Planning from public data first, then measuring on site, is how surveyors work. How accurate the elevations need to be depends on the job: a septic design needs the fall from the house to the tank and the field, and the rise to the field for a pump.

• Before the site visit, the public elevations give a working layout and show where the slope may be a problem.
• On site, measure the elevations that matter with a level, and enter them as level readings from a benchmark. Then click Recalculate in the elevation list.
• Any elevation can be typed over in the elevation list or in Details > Elevations.

Field-check the elevations

Public elevation data is accurate in some places and much less so in others. Treat every elevation the design starts with as something to check on site.