GPSHPositioningError (0x001F) says how far off the recorded position may be, in meters. A value of 4.7 means the device believed the real spot was within roughly 5 m of the GPS coordinates in the file. The tag was added in EXIF 2.3 (2010), when the spec started covering positions from Wi-Fi and cell towers, and holds one unsigned rational.
[GPS] GPSHPositioningError : 4.7 m
[GPS] GPSDOP : 1.2The "m" is ExifTool's display formatting; with -n you get the bare 4.7. The specification fixes the unit but not a confidence level, so read the number as the device's own estimate, not a guarantee.
It is horizontal only. EXIF has no matching tag for vertical error, so GPSAltitude comes with no accuracy figure at all, and altitude from a phone is usually worse than its horizontal position.
Error radius versus DOP
| Tag | ID | Unit | What it describes |
|---|---|---|---|
| GPSHPositioningError | 0x001F | meters | Estimated error radius |
| GPSDOP | 0x000B | none | Dilution of precision |
GPSDOP is the older tag and describes satellite geometry. A DOP of 1.2 means the satellites were well spread out, which is good, but it says nothing in meters and nothing about a fix computed from Wi-Fi or cell towers. When both tags are present, the error radius is the one to use.
Who writes it and what it is good for
iPhones write it next to the coordinates, so it shows up in most iPhone HEIC and JPEG files that have a location. Plenty of other cameras and Android apps leave it out. Its absence means nothing either way.
The practical use is filtering. Before plotting a few thousand photos on a map, drop the ones whose error is in the hundreds of meters: those positions came from a network fix, often indoors, and they scatter.
For privacy it cuts the other way. A small error tells anyone reading the file that the coordinates really are your doorstep. Clearing this tag alone changes nothing, since the position stays. The EXIF reader shows the value; the location removal guide explains how to drop the whole GPS block.