Geotrace – Nextra

The geotrace question type captures a sequence of geographic coordinates forming a line or path (polyline). In rtSurvey's web form, this renders as a text input where the enumerator enters or pastes the coordinate string directly.

Basic XLSForm Specification

type	name	label
geotrace	river_path	Trace the path of the river
geotrace	road_route	Record the road route

For the standard specification see the XLSForm documentation (opens in a new tab).

Data Format

Stored as a semicolon-separated list of points with no spaces around the semicolons. Each point is four space-separated values:

lat lon alt acc;lat lon alt acc;lat lon alt acc

Component	Description
`lat`	Latitude in decimal degrees
`lon`	Longitude in decimal degrees
`alt`	Altitude in metres (`0` if unknown)
`acc`	GPS accuracy in metres (`0` if unknown)

Example — a three-point path:

13.756331 100.501762 15 8;13.758000 100.503000 14 6;13.760000 100.505000 13 5

A minimum of two points is required to form a valid path.

How it renders in rtSurvey

In the rtSurvey web form, geotrace renders as a plain text field. The enumerator types or pastes the coordinate string. There is no built-in interactive map picker for this type in the current web form.

Collecting points interactively

The recommended pattern for field collection is a repeat group of geopoint questions — each point uses the full GPS map picker — combined with a calculate to produce the geotrace string:

type	name	label	calculation
begin repeat	path_points	Record each waypoint
geopoint	point	Tap to record point
end repeat	path_points
calculate	geotrace_value		`join(';', ${path_points/point})`

The calculated string can then be stored in a text question or used in geotrace.

Example usage

type	name	label	hint	required
geotrace	farm_boundary_path	Record the access path to the farm	Enter each waypoint separated by semicolons	yes

Best Practices

Use a repeat group of geopoint questions for interactive map-based collection, then join the values — this gives enumerators a GPS picker for each individual point.
Include the expected format in the hint column when manual coordinate entry is required.
Validate presence with required = yes when the path is mandatory.
Plan for data cleaning — paths entered manually may have inconsistent precision.

Limitations

There is no built-in interactive map picker for geotrace in the rtSurvey web form.
The coordinate string can be long for complex paths — keep this in mind for form performance and storage.
Validating path topology (e.g., minimum point count, self-intersection) requires post-processing outside of XLSForm constraints.

geopoint geoshape