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Country Coordinate Systems

KSA-GRF17: Saudi Arabia Geodetic Reference Frame

Updated · GeoCAD Bridge engineering team · 8 min read

Summary

KSA-GRF17 is the national geodetic reference frame of Saudi Arabia, defined by GEOSA and aligned to ITRF2014 at epoch 2017.0. It uses the GRS 80 ellipsoid. The geographic CRS is EPSG:9333 and projected UTM zones 36N to 40N are EPSG:9356 to EPSG:9360. KSA-GRF17 and current WGS 84 differ by a few decimetres at most (about 0.30 m at Riyadh using the EPSG transformation), unlike the legacy Ain el Abd 1970 datum, which differs by tens of metres.

Definition

KSA-GRF17: Kingdom of Saudi Arabia Geodetic Reference Frame 2017, a plate-fixed realization of ITRF2014 for Saudi Arabia on the GRS 80 ellipsoid.

  • Ellipsoid: GRS 80
  • Geographic 2D: EPSG:9333
  • Geocentric: EPSG:9331
  • UTM 36N–40N: EPSG:9356–9360
  • To WGS 84: EPSG op. accuracy 1 m

EPSG codes

KSA-GRF17 CRSs in the EPSG Dataset.
EPSGNameArea of use
9331KSA-GRF17 (geocentric)Saudi Arabia
9332KSA-GRF17 (geographic 3D)Saudi Arabia
9333KSA-GRF17 (geographic 2D)Saudi Arabia onshore and offshore
9356KSA-GRF17 / UTM zone 36NWest of 36°E
9357KSA-GRF17 / UTM zone 37N36°E – 42°E
9358KSA-GRF17 / UTM zone 38N42°E – 48°E
9359KSA-GRF17 / UTM zone 39N48°E – 54°E
9360KSA-GRF17 / UTM zone 40NEast of 54°E

KSA-GRF17 and WGS 84

The EPSG transformation “KSA-GRF17 to WGS 84 (1)” has zero translations and scale, and rotations of −0.008393″, +0.000749″ and −0.010276″ (position vector), with a stated accuracy of 1 m that reflects the uncertainty of the WGS 84 ensemble. For centimetre work, treat RTK network coordinates in KSA-GRF17 as the project datum and do not transform to “WGS 84” at all.

GeoCAD Bridge’s bundled definitions now apply these rotations exactly as EPSG/PROJ do; results agree with PROJ to better than 1 mm in automated tests.

KSA-GRF17 versus Ain el Abd 1970

Most older Saudi maps and engineering drawings use Ain el Abd 1970 on the International 1924 ellipsoid. At Riyadh the same point differs by about 67 m between Ain el Abd / UTM 38N and KSA-GRF17 / UTM 38N with the EPSG default transformation, whose accuracy is only 18 m. For legacy data use locally derived parameters from common control points.

Worked example

Riyadh (WGS 84 24.7136° N, 46.6753° E) in three Saudi CRSs, computed with PROJ.
CRSEPSGEasting (m)Northing (m)
KSA-GRF17 / UTM 38N9358669,459.8412,734,271.879
WGS 84 / UTM 38N32638669,459.6222,734,271.672
Ain el Abd / UTM 38N20438669,525.2112,734,259.173

FAQ

Is KSA-GRF17 the same as WGS 84?

Not exactly, but for mapping they agree to well within a metre. For survey-grade work, KSA-GRF17 is the authoritative national frame and should be used directly.

Which EPSG code should I use for Riyadh in KSA-GRF17?

EPSG:9358, KSA-GRF17 / UTM zone 38N.

How do I convert Ain el Abd coordinates to KSA-GRF17?

Use a transformation derived from common points in your project area. The EPSG 3-parameter transformation is only accurate to about 18 m.

Tools

Articles

References

  1. General Authority for Survey and Geospatial Information (GEOSA), Kingdom of Saudi Arabia. KSA-GRF17 reference frame documentation.
  2. IOGP. EPSG Geodetic Parameter Dataset, epsg.org.
  3. PROJ contributors. PROJ coordinate transformation software library, proj.org.

Cite this page

GeoCAD Bridge. “KSA-GRF17: Saudi Arabia Geodetic Reference Frame.” GeoCAD Bridge Knowledge Center, updated 2026-10-05. https://www.geocadbridge.com/knowledge/coordinate-systems-ksa-grf17/