Import & Reference Layers
Reference layers are GIS data you bring in to see under your survey: plot boundaries, road centrelines, a soil map, last year’s points. They are drawn on the map, can be tapped for their attributes, and travel with a survey when you export it — but they are never edited in Tavak.
Supported formats
| Format | What is read | Limits |
|---|---|---|
| GPX | Waypoints, routes and tracks | 5 MB per file; per layer 5 000 polygons, 10 000 lines or 15 000 points |
| GeoJSON | Feature / FeatureCollection; Multi* members become separate features; polygon holes kept; properties become attributes | |
| Shapefile (.zip) | .shp/.shx/.dbf, and the .prj for projected data (UTM, TM-3, any EPSG or WKT) | |
| KML / KMZ | Placemarks including MultiGeometry; ExtendedData becomes attributes | |
| CSV / Excel (.xlsx) | A point layer from two coordinate columns; you pick the columns and the app validates every row | |
| GeoPackage (.gpkg) | Feature tables only — you choose which tables become layers. Raster and tile tables are listed but greyed out. | 100 MB per file; the per-layer caps above; 30 000 features per import; 1 million vertices per layer |
| Vector Tiles (.mbtiles) | MVT/PBF tilesets, drawn from the tiles as you pan and zoom — see Basemaps & Offline Maps | No feature limit; storage only |
Importing a layer
- Open the Data tab and select Layers.
- Tap Add Layer and pick the format.
- Choose the file. Tavak checks it immediately — a wrong type, a file over the limit, or a shapefile ZIP missing its parts is reported here, not after a long import.
- Give the layer a name, then tap Import. Large files run in the background with progress; you can cancel.
Spreadsheets ask you to pick the latitude and longitude columns and show a summary of rows that could not be read before anything is imported. GeoPackages show every table in the file — name, geometry type, feature count and coordinate system — with a checkbox for each importable one; each selected table becomes its own layer named <file>: <table>.
Coordinate systems
Tavak stores everything in WGS 84. Data in a projected system is transformed on import:
- Shapefile — from the
.prj. Include it in the ZIP; without it, projected coordinates (large metre values) are refused with a message rather than plotted in the wrong place. - GeoPackage — from each table’s SRS: EPSG codes, UTM zones, Indonesian TM-3 and WKT definitions are handled automatically.
- When the system cannot be determined, a Coordinate System screen lets you search EPSG codes or pick a UTM zone. Recent choices are remembered.
Working with layers
Tap a layer card in Data › Layers for its options: show or hide it, zoom to its extent, change its style, or delete it. Swiping a card from right to left also deletes it.
Style sets the colour, line width, fill and point symbol. Large layers are simplified automatically at low zoom levels so panning stays smooth; the full geometry is drawn as you zoom in.
On the map, tapping a reference feature opens its attributes. Where several objects overlap, a list lets you pick the one you meant.
Layers and survey export
Reference layers that were visible during a survey are included in its export bundle, so the survey opens in QGIS with the same context. Layers imported from one GeoPackage share a single copy of the file in the bundle. Deleting a layer removes its file from the device once no other layer uses it.
Re-importing a survey
A survey exported from Tavak (ZIP or GeoPackage) can be imported on another device from the Survey tab. The importer verifies the bundle’s metadata, restores the session with its track, media, features, forms, destinations and reference layers, and reports anything it had to skip. Landmarks carried in the bundle that already exist on the device are not duplicated.
When it doesn’t work
- “Coordinates are not latitude/longitude”
- The shapefile is projected and the ZIP has no
.prj. Add it and import again. - The layer imported but nothing shows on the map
- Zoom to its extent from the layer options — it may simply be elsewhere. If it is empty, the file’s geometries could not be read (a curved-geometry GeoPackage, for instance, is refused by table with the reason shown in the picker).
- Import refused as too large
- Split the file, or simplify it in QGIS. The limits exist so the map stays usable on a phone.