Every tree on a plot, in one record.
Stem Mapper is a free iPhone app for forest inventory and research. It measures stems with the phone's LiDAR, records seedlings by hand, keeps every tree in a plot that can be mapped, remeasured and exported, and shows its work.
What it does
- Diameter at breast height from LiDAR. Aim at a trunk and tap. A circle is fitted to the bark and drawn on it, with the traced outline beside it, so a poor fit is visible on the spot and can be redone. The share of the circle seen and the fit error are kept with the measurement.
- Small trees too. Seedlings are placed on the map with root-collar diameter, height, planting date, damage and the cause of loss, and the same record grows into a measured stem in later years.
- Fixed-radius plots. Set a plot centre and size, from 0.01 ha to a quarter acre or any radius, and read stems per hectare and per acre, basal area, quadratic mean diameter and the species split.
- Maps. A plan view in metres and a satellite imagery view. Stems can be placed by hand, tied to earlier visits, and shifted together onto the imagery when the phone's GPS was off.
- Attributes a forester or researcher needs. Species, tape diameter for validation, tag, status, health, damage, competition, tree height and crown base, leaf samples, and the position of an increment core with bark and sapwood thickness.
- Open export. One CSV per plot with a column for everything, including the fit diagnostics and the outline polygon, that opens in any spreadsheet or GIS.
Getting it
Stem Mapper runs on an iPhone 12 Pro or any later Pro model, or an iPad Pro with LiDAR. It is in testing through TestFlight ahead of its App Store release. To join the test, write to the address on the support page.
Accounts and hosted plots
The app works entirely on the phone and needs no account. Plot hosting, sharing, a web map and shapefile and GeoJSON export are being built for this site. Private forestry use of those services will be by subscription; university researchers and some partner organisations will have free access.
Stem Mapper replaces ForestScanner for people who used it for stem measurement and need something that is maintained, keeps the whole plot, and records small trees.