GNSS RTK Surveying in Saudi Arabia: NGOSA CORS Guide 2026

Vision 2030 has committed over $1.1 trillion to infrastructure development across Saudi Arabia, spanning:

• NEOM: a 26,500 km² smart city development in the northwest, including THE LINE linear city, SINDALAH island resort, and TROJENA mountain development. Requires extensive topographic survey across challenging desert and mountain terrain.
• Red Sea Project: luxury resort development across 28 islands and 1,300 km of coastline. Coastal and marine survey demands.
• Diriyah Gate: historical restoration and new urban development northwest of Riyadh. Dense urban survey requirements.
• Road and rail network: 4,000+ km of new roads and high-speed rail corridors connecting major cities.
• Oil & gas infrastructure: continued expansion of Aramco upstream and downstream facilities across the Eastern Province.

For GNSS surveyors, this pipeline means sustained demand for equipment that handles Saudi Arabia's specific datum (GCS-80), integrates with the NGOSA CORS network, and performs reliably in high-temperature desert conditions where ambient temperatures regularly exceed 45°C.

Saudi Arabia uses the GCS-80 (Geographic Coordinate System 1980) datum, also known as SRCS (Saudi Revised Coordinate System) in some project documentation. Key facts:

DATUM PARAMETERS:

• Ellipsoid: GRS80
• Reference frame: aligned to ITRF at the epoch of adjustment
• Relationship to WGS84: GCS-80 and WGS84 are closely aligned but not identical. A direct WGS84 project will produce coordinate offsets — always select GCS-80 explicitly in your survey software.

PROJECTION:

• UTM (Universal Transverse Mercator) is the standard projection for most project work in Saudi Arabia.
• Zone 37N covers western Saudi Arabia (Jeddah, Mecca, Medina, NEOM corridor).
• Zone 38N covers central and eastern Saudi Arabia (Riyadh, Dammam, Eastern Province, Aramco facilities).
• Zone 39N covers the far eastern tip near the UAE border — used for some Aramco offshore projects.

IN APEKSURV:
Select GCS-80 / UTM Zone 37N or 38N in Project → Coordinate System. Do not use WGS84 as a substitute. For projects that specify "Saudi Grid" — confirm with the project engineer whether this refers to GCS-80 UTM or a local project grid, as both are commonly used.

NGOSA (National Geospatial Authority of Saudi Arabia, formerly MOMRA Survey) operates the national CORS network across Saudi Arabia. Key facts:

NETWORK COVERAGE:
The NGOSA CORS network provides coverage across all major populated and industrial areas of Saudi Arabia. Coverage density is highest in the Central, Western, and Eastern Provinces. Remote desert areas (Rub' al Khali / Empty Quarter) may have limited coverage — check NGOSA station maps before mobilising to remote project sites.

REGISTRATION:
CORS credentials are obtained through NGOSA. Registration is required — credentials are not publicly available without account creation. Contact: National Geospatial Authority, Ministry of Municipal, Rural Affairs and Housing. Website: ngosa.gov.sa

NTRIP SERVER DETAILS:

• Server address: ngs.ngosa.gov.sa
• Port: 2101
• Format: RTCM 3.x (multi-constellation)
• Mountpoints: named by station location (e.g., RIYA for Riyadh, JEDD for Jeddah)

BASELINE RECOMMENDATION:
Select the mountpoint nearest to your survey site. For reliable Fixed solution, stay within 50 km of the selected reference station. In areas between stations more than 70 km apart, deploy an APEKS local base station on a known control point.

Saudi Arabia uses a national geoid model for converting GNSS ellipsoidal heights to orthometric heights referenced to mean sea level. This is critical for:

• Drainage and stormwater design (slope calculations)
• Road profile and vertical alignment
• Pipeline elevation control
• Building finished floor levels

WITHOUT GEOID MODEL: GNSS elevation output is ellipsoidal height above the GRS80 ellipsoid. In Saudi Arabia, the difference between ellipsoidal height and orthometric height (geoid separation / N value) varies by region: approximately +15 m to +25 m across most of the country. Using ellipsoidal heights directly in design software will introduce systematic elevation errors of this magnitude.

IN APEKSURV: Apply the Saudi Arabia national geoid model in Project → Coordinate System → Geoid Model. APEKS receivers include the Saudi Arabia geoid model in the pre-loaded coordinate library. Select it explicitly — do not use the global EGM2008 model as a substitute for the national model on precision projects.

VERIFICATION: At the start of every session, check RTK elevation against a levelled benchmark. The difference should be within ±25 mm. If it exceeds 50 mm, recheck the geoid model selection.

1. NEOM AND MEGA-PROJECT LAYOUT: The scale of NEOM and THE LINE requires GNSS survey for control network establishment, topographic mapping, and construction layout across desert, mountain, and coastal terrain. APEKS AP80 Pro and AP60 Vision are deployed on NEOM project surveys for their full-constellation 1408-channel tracking and calibration-free IMU for work on steep terrain and in confined construction areas.
2. OIL & GAS INFRASTRUCTURE: Aramco and downstream operators require GNSS survey for pipeline route surveys, facility layout, and as-built documentation across the Eastern Province. IP67/IK08 receiver rating is essential for dusty desert environments.
3. ROAD AND HIGHWAY ALIGNMENT: Saudi Arabia's road expansion programme requires continuous GNSS survey for alignment, earthworks volume calculation, and setting out. RTK with 120° IMU tilt allows efficient slope stake setting without levelling the pole on embankment faces.
4. CADASTRAL AND BOUNDARY SURVEY: Rapid urban expansion in Riyadh, Jeddah, and new cities requires boundary demarcation at cadastral accuracy.
5. UTILITY AND DRAINAGE NETWORKS: Stormwater drainage design in low-relief desert terrain requires precise elevation control — geoid model accuracy is critical for these applications.