Terra assigns every location in the Kingdom — from a doorstep in Riyadh to an oil field in the Empty Quarter — a precise, permanent hexagonal address. A single open system connecting land, government, industry, logistics, and every citizen service on one universal spatial grid.
Terra is an open-source hierarchical geospatial indexing system. It divides Saudi Arabia into a nested grid of regular hexagonal cells, each uniquely identified by a compact numeric code. Think of it as a universal address system for space itself — one that works in deserts, cities, at sea, underground, and in the air.
Unlike a street address, which is tied to infrastructure that may not exist, a Terra cell exists everywhere — even in uninhabited desert, remote coastline, or mid-construction megaprojects. Unlike GPS coordinates, which are raw numbers with no context, a Terra cell carries hierarchy: every cell knows its parent region, its neighbouring cells, and its children.
Terra cells are hexagonal because hexagons tile a plane with equal-distance neighbours — each of the six adjacent cells is the same distance from the centre. This makes spatial analysis simpler, more consistent, and more accurate than square grids, where corner neighbours are farther away than edge neighbours.
Every Terra cell sits at one of 15 resolution levels. Moving one level coarser multiplies the cell area by 7 (aperture-7 hierarchy). Resolution 8 — the 1-hectare base cell — is the national standard anchor.
| Res | Name | Cell edge | Cell area | Cells in KSA | Primary use |
|---|
Saudi Arabia has undergone rapid spatial development — yet the foundational data infrastructure connecting government ministries, private enterprises, and citizens remains fragmented. Terra addresses four core problems.
Terra is designed to serve a wide range of audiences — from government ministries needing a compliant national standard, to mobile developers building location-aware applications.
Terra provides the common spatial language that connects each of these sectors to one another. A logistics zone, an agriculture permit, an emergency dispatch area, and an environmental monitoring point all reference the same underlying grid.
Most spatial data cannot be fed to a model without weeks of preparation. Boundaries disagree, areas differ, projections conflict, and every join is a geometric operation. Indexed to Terra, location becomes an integer key and the grid becomes a table — one row per cell, one column per dataset. The preparation step largely disappears.
Every Terra cell has two human-readable string representations. The Terra Index String (TIS) is the low-level form used by code and databases. The Terra Grid Code (TGC) is the human-readable form — compact, resolution-explicit, with no administrative boundary reference. Both strings represent the same cell and convert between each other with pure arithmetic. No lookup table, no network call needed.
| Resolution | Terra Index String (TIS) | TIS length | Terra Grid Code (TGC) | TGC length | Cells at this resolution |
|---|---|---|---|---|---|
| Res 0 | t10085ffffffffff8 | 17 | T00-22T | 7 | ~37 national tiles |
| Res 2 | t102858fffffffff8 | 17 | T02-45HG | 8 | ~1,800 cells |
| Res 4 | t104858ddfffffff8 | 17 | T04-8B3E3 | 9 | ~89,000 cells |
| Res 6 | t106858dc87fffff8 | 17 | T06-GP6WG0 | 10 | ~4.4M cells |
| Res 8 ★ | t108858dc825ffff8 | 17 | T08-11CDS0J0 | 12 | ~215M cells (1 ha) |
| Res 10 | t10a858dc82427ff8 | 17 | T10-22RVJ144B | 13 | ~10.5B cells |
| Res 12 | t10c858dc824215f8 | 17 | T12-45HQ4288A3 | 14 | ~516B cells |
| Res 14 | t10e858dc82421520 | 17 | T14-8B3E84GGN45 | 15 | ~25T cells |
SANSRS — the Saudi Arabia National Spatial Reference System — defines the legal coordinate framework for all surveys and geospatial activities in the Kingdom. Terra is natively built on SANSRS components. No conversion layer, no approximation.
| EPSG code | Name | Description | Terra usage |
|---|---|---|---|
| 9333 | KSA-GRF17 geographic 2D | Primary horizontal datum — lat/lng on GRS 1980 ellipsoid anchored to ITRF2014 epoch 2017.0 | Primary input |
| 9332 | KSA-GRF17 geographic 3D | Horizontal + ellipsoidal height; used when accepting GNSS observations from KSA-CORS | 3D input |
| 9356 – 9360 | KSA-GRF17 / UTM zone 36N–40N | KSA-GRF17 in projected UTM coordinates — five zones covering Saudi territory | Accepted input |
| 9335 | KSA-VRF14 height | Orthometric height above mean sea level at the Jeddah Tide Gauge (Helmert-Orthometric) | Vertical datum |
| 9520 | KSA-GRF17 + KSA-VRF14 height | Compound CRS combining horizontal GRF17 and vertical VRF14 — the complete 3D SANSRS | 3D cell CRS |
| 10776 | KSA-GRF17 → KSA-VRF14 (KSA-GEOID21) | Geoid model transformation (KSA-GEOID21.gra) — 1.5 cm accuracy. Converts GNSS ellipsoidal height to orthometric height for 3D Terra cells | Geoid transform |
Terra includes built-in Helmert transformation parameters for all four historical KSA reference frames: GDMS (0.6 m shift), MTRF-2000 (0.6 m), ARAMCO WGS84 (0.8 m), and Ain Al Abd (93 m grid transformation). Organisations migrating to SANSRS can simultaneously re-index their spatial data into Terra.
The 200+ active KSA-CORS stations operated by GEOSA provide real-time KSA-GRF17 positioning. A field surveyor's GNSS receiver outputs KSA-GRF17 coordinates directly, which feed into Terra without any conversion step. RTK precision to 1–2 cm maps to sub-cell accuracy at Res 9 (23 m cells).