How to Make a Contour Map from Survey Data

Reference

Between a page of surveyed numbers and a finished contour map sit three decisions: how to clean the data, how to grid it, and how to present it. This guide walks all three with free browser tools, whether the values are elevations, water levels, formation tops, or grades.

Step 1: Clean the file

Field data arrives with mixed delimiters, duplicate points, header lines, and notes in the middle. Run it through the CSV Cleaner first: delimiters unify, junk drops, duplicates collapse, and the counters tell you exactly what was removed. A map built on dirty data inherits every flaw invisibly.

Step 2: Grid it honestly

Paste the clean points into the Contour Map Generator. Inverse distance weighting fills the grid: power 2 is the standard, higher powers honor local data more tightly, and the grid resolution trades smoothness for speed. Know the limits: IDW never extrapolates beyond your data range and makes bulls eyes around isolated extremes, which is a feature when you want the data respected and a flaw when you want geology imagined.

Step 3: Choose the interval and colors

The auto interval gives about ten contours at a round number; survey standard work wants explicit choices like half meter water tables or five meter topography. Terrain colors suit elevations, the blue ramp suits water, and the thermal ramp suits grades. Click anywhere on the map to read the interpolated value before you trust it.

Step 4: Export and use

Download the PNG for documents or print the report for the file. The same clean grid feeds the Earthworks Volume Calculator for cut and fill, and water level maps pair with the Pumping Test Analysis Tool that produced the levels.

The judgment calls

  • Point density beats interpolation cleverness: five more measurements outperform any power setting.
  • Map the data you have, not the surface you expect; the gaps are information.
  • State the method on the figure: a map that hides how it was gridded invites more trust than it earned.

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