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Units & Coordinates

The Units & Coordinates settings control how positions, distances, and areas are displayed throughout Mapit GIS. You can choose from several coordinate formats, set a custom EPSG projection code, and configure measurement units.

Go to Settings > Units & Coordinates to access these options.

Coordinate system​

Select how coordinates are displayed on the map, in feature lists, and during data export.

OptionFormatExample
WGS84 (D.dddd)Decimal degrees51.50134, -0.12797
WGS84 (D M.mm)Degrees decimal minutes51 30.08040' N, 0 7.67838' W
WGS84 (D M'S.ss)Degrees minutes seconds51 30' 04.824'' N, 0 7' 40.703'' W
Web MercatorEPSG:3857 metres3857285.42, -14245.67
British National GridEPSG:27700 metres530034.000, 179706.000
UTM ETRS89Auto-detected UTM zone33U 456789.12, 5678901.23
UTM (MGRS)NATO Military Grid33UVP 56789 78901
Custom EPSGAny supported codeUser-defined

Custom EPSG code​

Select Custom: EPSG code and enter any EPSG code supported by the projection library. This is useful for national or regional coordinate systems not listed in the preset options. The app supports thousands of EPSG codes - if the code is invalid or unsupported, you will see an error and the system reverts to WGS84.

Length unit​

Choose the unit for distance measurements and line lengths:

  • Meters (m)
  • Yards (yd)
  • Kilometers (km)
  • Miles (mi)
  • Feet (ft)
  • Nautical miles (nmi)
  • Sazhen (saz)

Area unit​

Choose the unit for polygon area calculations:

  • Square meters (m2)
  • Hectares (ha)
  • Ares (a)
  • Square kilometers (km2)
  • Square miles (mi2)
  • Acres (ac)
  • Square feet (ft2)
  • Square nautical miles (nmi2)
  • Square sazhen (saz2)
  • Chinese Mu

High-accuracy CRS grids​

Pro Plus feature

High-accuracy CRS grids require a Mapit Pro Plus subscription.

Android only

High-accuracy CRS grids are currently available on Android only. iOS support is planned for a future release.

When you select a coordinate system that has a compatible datum transformation grid, a High-Accuracy Datum Grid option appears in the settings. These grids provide centimetre-level coordinate accuracy by replacing the default mathematical datum transformation (TOWGS84 parameters) with a dense grid of measured corrections.

How it works​

Without a grid, coordinate transformations between local datums and WGS84 use a 3 or 7-parameter Helmert transformation. This gives typical accuracy of 2-10 metres depending on the datum. With a grid enabled, the transformation uses thousands of surveyed control points interpolated across the coverage area, achieving sub-metre or even centimetre-level accuracy.

The grid correction is applied automatically to:

  • Map display - coordinates shown on screen
  • Feature selection - coordinates in the feature details sheet
  • Import - shapefiles and other files in the local projection
  • Export - data exported to the local projection
  • Edit geometry - manual coordinate entry
  • Search - coordinate search in the local projection

Downloading and enabling a grid​

  1. Select a supported coordinate system (preset or custom EPSG code)
  2. The High-Accuracy Datum Grid section appears below the coordinate system selector
  3. Tap Download Grid to download the grid file to your device
  4. Toggle Use high-accuracy grid to enable the correction

Grid files are downloaded once and stored locally. They range from 59 KB to 51 MB depending on the country and grid density.

Supported grids​

CountryGridEPSG codesSize
United KingdomOSTN15 (OSGB36 to ETRS89)2770015 MB
PortugalDatum 73 to ETRS89274931 MB
PortugalDatum Lisboa to ETRS89207901 MB
FranceNTF to RGF9327561-27564, 27571-27574271 KB
GermanyDHDN BeTA2007 to ETRS8931466-3146982 KB
SpainED50 to ETRS8923028-23031varies
NetherlandsAmersfoort/RD to ETRS892899259 KB
BelgiumBD72 to ETRS89313705.3 MB
SwitzerlandCH1903 to CH1903+217813.2 MB
ItalyRoma40 to WGS843003, 3004973 KB
IcelandISN93 to ISN201630572.0 MB
LatviaLKS-92 to LKS-20203059538 KB
Czech RepublicS-JTSK corrections5514, 5513, 2065286 KB
SlovakiaS-JTSK corrections5514, 5513, 2065682 KB

Grid sources​

All grids are derived from official geodetic authority data:

  • UK: Ordnance Survey
  • Portugal: DGT (Direcao-Geral do Territorio)
  • France: IGN (Institut Geographique National)
  • Germany: AdV/BKG (Bundesamt fur Kartographie und Geodasie)
  • Netherlands: NSGI (Netherlands Partnership of Geodetic Infrastructure)
  • Belgium: IGN Belgium (Institut Geographique National)
  • Switzerland: swisstopo (Federal Office of Topography)
  • Italy: IGM (Istituto Geografico Militare)
  • Iceland: LMI (Landmaelingar Islands)
  • Latvia: LGIA (Latvian Geospatial Information Agency)
  • Australia: ICSM (Intergovernmental Committee on Surveying and Mapping)
  • New Zealand: LINZ (Land Information New Zealand)
  • USA: NOAA/NGS (National Geodetic Survey)
  • Canada: NRCan (Natural Resources Canada)
  • Czech Republic: CUZK (Czech Office for Surveying, Mapping and Cadastre)
  • Slovakia: UGKK (Geodetic and Cartographic Institute)

Technical details​

The app uses two types of correction grids:

NTv2 grids (UK, Portugal, France, Germany, Spain, Netherlands, Belgium, Switzerland, Italy, Iceland, Latvia, Australia, New Zealand, USA, Canada) operate in geographic coordinate space. They store latitude and longitude shifts in arcseconds at regular grid intervals. The app performs bilinear interpolation between grid nodes for sub-grid accuracy. For export (WGS84 to local datum), an iterative inverse transform converges to sub-millimetre precision in 3 iterations.

Projected-space grids (Czech Republic, Slovakia) store easting and northing corrections in metres, applied directly to Krovak projected coordinates. These use bilinear interpolation on a regular grid in the projected coordinate space.