PPM is an abbreviation for “parts per million”. In surveying, it is a unit of measurement that surveying equipment manufacturers use to express the accuracy of their measuring equipment.
For example, if a total station has a stated distance measurement error of 1ppm, this means that for every million millimeters (1,000 meters / 1 kilometer), there will be 1 millimeter of error, or another way to state it is for every 1 kilometer, there will be 1 millimeter of error.
Some examples of total station manufacturers’ distance accuracies:
| Total Station | Manufacturers stated distance error | PPM over 1km | Total distance error over 1km | Total distance error over 5km |
|---|---|---|---|---|
| Leica TS16 | +/- 1.0 mm + 1.5ppm | PPM (1km) = 1.5mm | +/- 1.0 mm + 1.5 mm, or +/- 2.5mm | +/- 1.0 mm + 7.5 mm, or +/- 8.5mm |
| Trimble S9 | +/- 1.0mm + 2.0ppm | PPM (1km) = 2.0mm | +/- 1.0 mm + 2.0 mm, or +/- 3.0mm | +/- 1.0 mm + 10.0 mm, or +/- 11.0mm |
| Topcon GT-1200/600 | +/- 1.0mm + 2.0ppm | PPM (1km) = 2.0mm | +/- 1.0 mm + 2.0 mm, or +/- 3.0mm | +/- 1.0 mm + 10.0 mm, or +/- 11.0mm |
Some examples of GNSS manufacturers’ distance accuracies:
| GNSS | Manufacturers stated horizontal error (RTK) | PPM over 1km | Total distance error over 1km | Total distance error over 5km |
|---|---|---|---|---|
| Leica GS18 | +/- 8.0mm + 1.0ppm | PPM (1km) = 1.0mm | +/- 8.0 mm + 1.0 mm, or +/- 9.0mm | +/- 8.0 mm + 5.0 mm, or +/- 13.0mm |
| Trimble R10 | +/- 8.0mm + 1.0ppm | PPM (1km) = 1.0mm | +/- 8.0 mm + 1.0 mm, or +/- 9.0mm | +/- 8.0 mm + 5.0 mm, or +/- 13.0mm |
| Topcon HiPer | +/- 5.0mm + 0.5ppm | PPM (1km) = 0.5mm | +/- 5.0 mm + 0.5 mm, or +/- 5.5mm | +/- 5.0 mm + 2.5 mm, or +/- 7.5mm |
FAQs
What is 1ppm in surveying?
If the manufacturer states that the distance error of the instrument is 1ppm, then that is equal to 1mm per 1km.
What is 2ppm in surveying?
If the manufacturer states that the distance error of the instrument is 2ppm, then that is equal to 2mm per 1km.
What is 5ppm in surveying?
If the manufacturer states that the distance error of the instrument is 5ppm, then that is equal to 5mm per 1km.