GPS Tracking & Field Collection¶

GeoLibre has two tools for work in the field, both on the Controls menu:

• GPS Tracking... streams a live position onto the map, records a track log, and captures points where you stand.
• Field Collection... captures point, line, or polygon observations against a form you define, with optional photos.

Both write ordinary GeoJSON layers, so everything they capture is saved with the project, shows up in the attribute table, and exports through the usual Layer actions → Export formats. Neither has a server sync or upload step: captures live in the project until you save or export it.

GPS Tracking¶

Controls → GPS Tracking... opens the GPS Tracking dialog.

Position source¶

Pick one entry under Position source:

• This device uses the browser or operating system's location service with high accuracy requested. In the Android and iOS apps the OS asks for location permission the first time. If permission is refused the dialog says so; allow location for the site (browser) or app (system settings) and press Start GPS again.
• NMEA receiver (serial or Bluetooth) reads an external GPS/GNSS receiver. Choose a Baud rate (4800, 9600, 19200, 38400, 57600, or 115200; 9600 by default, and remembered), then Connect serial or Connect Bluetooth. Once connected the dialog shows the device and a running count such as 1,204 sentences · 300 fixes with the current fix quality (for example RTK fixed, RTK float, Differential GPS). Disconnect releases the receiver.

GeoLibre parses the GGA, RMC, VTG, GSA, and GST sentences from any talker (GP, GN, GL, …). Accuracy comes from GST when the receiver sends it; otherwise it is estimated from HDOP.

Following your position¶

Start GPS begins streaming. The map shows a blue dot, a heading arrow when a heading is reported, and a translucent circle for the reported accuracy. The readout lists the accuracy (±4 m), Satellites, altitude, speed in km/h, and heading in degrees.

Keep map centered on my position (on by default) recenters the map on each fix. Dragging the map turns it off.

When you close the dialog while GPS is running, a small floating panel stays in the bottom corner of the map with the coordinates, accuracy, satellites, speed, the track statistics, Capture point, a follow toggle, Pause/Resume, and a button that reopens the dialog.

Recording a track¶

Under Track log:

1. Record track clears any previous unsaved track and starts recording, turning GPS on if needed.
2. Pause stops logging; Resume continues in a new segment, so a gap is not drawn as a straight line.
3. While a track exists the dialog shows its point count, distance, and duration, with four actions:
   • Save as layer adds the track to the project as a line layer named like GPS Track 2026-10-04 0930 (a MultiLineString when it has several segments), keeping each vertex's time, accuracy, and satellite count.
   • Export GPX writes GPX 1.1, one <trkseg> per segment.
   • Export GeoJSON writes the same track as GeoJSON.
   • Discard throws the track away.

Saving and exporting need at least two points.

Capturing points¶

Capture point under Digitize adds a point at the current fix to a layer named GPS Points, creating it on first use. Each point records time, accuracy_m, satellites_used, ele, speed_mps, and heading_deg. To capture into a layer of your choice, with a form, use Field Collection instead.

Logging filters¶

Each is off at 0. The filters are remembered between sessions.

Field Collection¶

Controls → Field Collection... captures observations into a collection layer against a custom form.

Set up a collection layer¶

1. Under Collection layer, pick an existing collection layer or New collection layer….
2. For a new layer, enter a Layer name and pick a Geometry: Point, Line, or Polygon. A layer holds one geometry type.
3. Add field for each attribute. Give it a Label, a Type (Text, Number, Date, or Choice), tick Required if it must be filled, and for a Choice field list the Options (comma-separated).
4. Create layer.

A layer with no fields captures location-only observations. Property names are derived from the labels. Fields have no default values.

If the layer has an attribute form configured, Field Collection uses it instead of the plain field list: its aliases, dropdowns and checkboxes, number, range and date widgets, conditional visibility, and constraints all apply.

Capture an observation¶

For a point:

• Use GPS takes a single high-accuracy fix from this device (up to 15 seconds). It does not read the NMEA receiver connected in GPS Tracking.
• Pick on map places the point where you click; Esc cancels.
• Reposition point moves a point you have already placed.

For a line or polygon, Draw on map opens a toolbar along the bottom of the map. Click to add vertices, or Add GPS vertex to add one at your current position; Undo removes the last vertex, and Finish (or a double-click) closes the shape once it has enough vertices.

Fill in the form, attach photos if you like, and press Save point, Save line, or Save polygon. Required fields are marked *, and the form refuses an empty required field, a non-numeric number, or a choice outside the listed options.

Photo (optional) → Choose photo… attaches one or more images, up to 2 MB each. Photos are stored on the feature, so they travel with the project.

Session behavior¶

Done ends the collection session. Closing the dialog with the X button or Esc only hides it: an Open Field Collection pill stays on the map so you can capture the next observation without setting up again.

The GPS accuracy shown while collecting is for your information and is not stored on the feature. If you need per-point accuracy and satellite counts, use Capture point in GPS Tracking.

Working offline¶

Captures are kept in the project, so collecting needs no connection once the app is loaded. Cache the basemap for the area before you go with Project → Offline Basemap..., and save the project before closing the app.