GNSS Surveying in Saudi Arabia: NGOSA CORS, SRCS2000 & RTK Guide
RTK GNSS survey in Saudi Arabia uses the SRCS2000 coordinate system (based on ITRF2000, epoch 2000.0) and the NGOSA CORS network for NTRIP corrections. NGOSA coverage is concentrated in urban centres — Riyadh, Jeddah, Dammam — and thins significantly across desert infrastructure corridors, remote pipeline routes, and rural project areas. For sites beyond reliable NGOSA coverage, deploy a local base+rover configuration: any AP10 or AP20 as a lightweight base on a known control point, or a MAX5 dedicated base station with 5W LoRa and 25 km range. No internet, no CORS subscription required. All APEKS receivers use international firmware with no geo-fence restrictions — firmware updates work identically in Saudi Arabia as in any other country.
- Saudi Arabia GNSS Survey Overview
- SRCS2000 — The Saudi Coordinate System
- NGOSA CORS Network — Coverage and Limitations
- Connecting to NGOSA via NTRIP
- When NGOSA Is Not Available — Base+Rover Approach
- The Core Challenges in Saudi Arabia GNSS Survey
- Recommended Equipment for Saudi Arabia
- Field Deployment Scenarios
- FAQ
Saudi Arabia GNSS Survey Overview
Saudi Arabia operates the SRCS2000 (Saudi Reference Coordinate System 2000) as its national geodetic datum, maintained by the General Authority for Statistics and the National Center for Spatial Information (NCSI, formerly MOMRA). The NGOSA CORS network (National Geodetic Office of Saudi Arabia) provides NTRIP-based RTK corrections in covered areas.
KEY FACTS FOR FIELD SURVEYORS:
- National coordinate system: SRCS2000
- Reference frame: ITRF2000, epoch 2000.0
- Ellipsoid: GRS80
- Projection: UTM (Universal Transverse Mercator)
- UTM Zone 36N covers western Saudi Arabia (Makkah, Madinah)
- UTM Zone 37N covers central Saudi Arabia (Riyadh, Qassim)
- UTM Zone 38N covers eastern Saudi Arabia (Dammam, Al-Khobar)
- Geoid model: SAGEOID17 (Saudi Arabia geoid)
- NTRIP protocol: v1 and v2 supported by all modern Chinese RTK receivers
SRCS2000 — The Saudi Coordinate System
SRCS2000 is Saudi Arabia's national spatial reference system, replacing the earlier Ain El Abd 1970 (AEA70) datum used in legacy cadastral and oil industry mapping. Modern construction and infrastructure projects require SRCS2000 coordinates. Legacy projects based on AEA70 require a datum transformation — your RTK field software (ApekSurv) must have the correct transformation parameters loaded before field work begins.
SRCS2000 SETUP IN ApekSurv:
- Select coordinate system: SRCS2000 / ITRF2000
- Confirm UTM zone for your project area:
- Zone 36N: western Saudi Arabia (longitude 30°E–36°E)
- Zone 37N: central Saudi Arabia (longitude 36°E–42°E)
- Zone 38N: eastern Saudi Arabia (longitude 42°E–48°E)
- Load SAGEOID17 geoid model for correct ellipsoidal to orthometric height conversion
- Verify with a known control point before commencing field observations
AEA70 TO SRCS2000 TRANSFORMATION:
If your project control points are in AEA70 (common in older oil industry surveys), apply the Helmert 7-parameter transformation. Contact the project's geodetic consultant for the specific parameters applicable to your project area. Do not apply a generic transformation without verification on local control.
NGOSA CORS Network — Coverage and Limitations
NGOSA (National Geodetic Office, Saudi Arabia) operates a permanent CORS network across the Kingdom providing NTRIP RTK corrections. The network supports both RTCM 2.x and RTCM 3.x correction formats and is accessible via standard NTRIP credentials issued through the NCSI.
COVERAGE ASSESSMENT:
NGOSA coverage is strongest in the main urban centres and degrades significantly across the desert interior and remote infrastructure corridors. Survey teams should verify NGOSA coverage for their specific project area before mobilising, as baseline distances beyond 50–70 km from the nearest CORS reference station will degrade RTK Fixed solution reliability.
| Region | City / Area | NGOSA Coverage | Recommended Approach |
|---|---|---|---|
| Central Region | Riyadh, Qassim | Good | NTRIP via NGOSA |
| Western Region | Jeddah, Makkah, Madinah, NEOM coast | Moderate | NTRIP where available; base+rover for remote areas |
| Eastern Region | Dammam, Al-Khobar, Al-Ahsa | Good | NTRIP via NGOSA |
| Northern Region | Tabuk, Ha'il, Al-Jouf | Limited | Base+rover recommended |
| Southern Region | Abha, Jizan, Najran | Limited | Base+rover recommended |
| Desert corridors | NEOM inland, pipeline routes, desert infrastructure | Sparse / absent | Base+rover with MAX5 required |
| Vision 2030 remote sites | NEOM mountain/desert, Red Sea islands | Absent | MAX5 base+rover essential |
Connecting to NGOSA via NTRIP
Register with NCSI (National Center for Spatial Information) to obtain NGOSA NTRIP access credentials: caster address, port, mountpoint, username, and password. Contact NCSI via their official portal for current registration procedure.
Open ApekSurv → Settings → Communication → NTRIP. Enter caster IP, port, and credentials. Select the mountpoint nearest to your project area. Confirm RTCM format (3.x preferred for modern receivers).
After NTRIP connection is established, wait for Fixed solution — typically 10–30 seconds on a clear-sky site. Confirm solution status shows Fixed (not Float) before recording any observation.
Occupy a known Saudi Geodetic Survey (SGS) control point and compare the RTK coordinate with the published value. Acceptable tolerance is ±20mm H for standard infrastructure work. Investigate any discrepancy exceeding 50mm before proceeding.
Keep the display showing distance to nearest CORS reference station. If baseline exceeds 50 km, expect degraded accuracy. If baseline exceeds 70 km, switch to base+rover configuration.
When NGOSA Is Not Available — Base+Rover Approach
For project areas beyond reliable NGOSA coverage — desert infrastructure corridors, remote pipeline routes, NEOM inland zones, and southern region sites — the base+rover configuration provides full RTK accuracy from a self-contained correction source.
LIGHTWEIGHT BASE (AP10 OR AP20):
Deploy any AP10 or AP20 on a known control point (SGS monument or established project control). Configure as base station in ApekSurv. The receiver broadcasts corrections via built-in 2W UHF radio to the rover within 8–15 km. Suitable for project areas up to 15 km radius from the base position. No SIM card, no internet, no NGOSA subscription required for the correction link.
MAX5 DEDICATED BASE STATION FOR LARGE DESERT SITES:
Deploy the MAX5 on a central control monument. 5W LoRa radio broadcasts corrections up to 25 km across flat desert terrain — significantly further than UHF in open, low-obstruction desert environments. 13,200 mAh internal battery operates for 8+ hours without external power. No external radio amplifier required. Multiple rovers receive corrections from the same MAX5 simultaneously — suited for large infrastructure corridor projects with multi-team operations. The MAX5 OLED display shows satellite count, battery status, and differential age without requiring a controller.
The Core Challenges in Saudi Arabia GNSS Survey
Symptom: Vision 2030 projects — pipeline corridors, road construction in the desert interior, utility infrastructure across the Empty Quarter approaches — are located far from NGOSA reference stations. The survey team attempts NTRIP connection, achieves Float solution only, and cannot get reliable Fixed. Field productivity drops to near zero as the team troubleshoots a CORS connection that will never be adequate for the site.
Cause: NGOSA network density is designed for urban and semi-urban survey demand. Desert infrastructure corridors can be 100–200 km from the nearest CORS station — well beyond the 50 km reliable baseline limit for RTK Fixed solution.
Fix: Deploy MAX5 base station on the nearest established Saudi Geodetic Survey (SGS) control point. 5W LoRa covers up to 25 km across flat desert terrain from one base position. For project corridors longer than 25 km, establish intermediate control and leap-frog the base along the corridor. Full RTK Fixed accuracy is maintained throughout.
Symptom: Summer temperatures in Saudi Arabia regularly exceed 45°C in the field. Equipment that performed reliably in Europe or Southeast Asia shuts down or gives erratic readings. Sand and dust ingress into connectors causes intermittent failures. Batteries drain faster in extreme heat, shortening field sessions.
Cause: Most RTK receivers specify operating temperature to +65°C, but internal component temperatures on a receiver mounted on a tripod in direct Saudi summer sun can exceed this. Connectors without IP67 protection allow fine desert sand to ingress over time, causing contact failures.
Fix: APEKS receivers carry IP67 dust and water protection and IK08 impact rating. Operating temperature is specified to +75°C. Port covers must be used consistently to protect connectors from fine desert sand. Battery performance in extreme heat can be managed by starting field sessions early morning and using shade protection for base station equipment during midday periods.
Symptom: The project's as-built drawings are in Ain El Abd 1970 (AEA70). The new infrastructure design is in SRCS2000. The survey team sets up in SRCS2000, occupies a legacy control point, and finds a 10–30 metre horizontal discrepancy. The team assumes equipment error and spends hours troubleshooting a hardware problem that does not exist.
Cause: AEA70 and SRCS2000 are different datums with a significant horizontal shift that varies across the Kingdom — typically 5–30 metres depending on location. Any coordinate comparison between the two datums without applying the correct 7-parameter transformation will show this discrepancy.
Fix: Before field work, confirm which datum all control points are published in. If mixing AEA70 and SRCS2000 control on the same project, obtain the project-specific Helmert transformation parameters from the geodetic consultant. Load these into ApekSurv's coordinate system settings. Verify the transformation on at least two independent control points before proceeding with production survey.
Recommended Equipment for Saudi Arabia
Equipment selection for Saudi Arabia survey should account for three factors absent in most other markets: potential NGOSA coverage gaps requiring base+rover deployment, extreme temperature and dust conditions requiring IP67+ protection, and large project areas requiring long-range correction broadcast.
| Instrument | Role | Key Spec | Saudi Arabia Application |
|---|---|---|---|
| AP20 | Standard rover or lightweight base | 1408ch, 120° IMU, 2W UHF, IP67/IK08 | General survey rover; configures as base on control point for CORS-denied sites |
| AP20 AR | AR stakeout rover | 1408ch, 120° IMU, bottom 5MP camera, IP67/IK08 | Construction stakeout on Vision 2030 infrastructure sites; AR overlay in dense layout grids |
| AP40 Laser+ | Laser offset + AR stakeout | 1408ch, 120m laser, IP67/IK08 | Highway cross-sections, utility corridor survey, inaccessible features across desert terrain |
| AP80 Pro | ALL IN ONE flagship | 1408ch, 120m laser, visual measurement, AR, IP67/IK08 | Complex infrastructure sites; laser + visual measurement where features span both hazardous and photogrammetric scenarios |
| MAX5 | Long-range desert base station | 5W LoRa, 25km, 13200mAh, OLED, IP67/IK08 | Remote desert sites, Vision 2030 corridors, pipeline routes beyond NGOSA coverage |
| APS1 | Lightweight handheld RTK | 1408ch, 60° IMU, 210g, IP67 | GIS data collection, asset inventory, utility mapping alongside main survey operations |
All APEKS receivers use international firmware with no geo-fence restrictions. Firmware updates via OTA work identically in Saudi Arabia as in any other country — no Chinese server dependency, no VPN required.
Field Deployment Scenarios
SCENARIO 1 — RIYADH URBAN CONSTRUCTION (NGOSA AVAILABLE):
AP20 AR rover connected to NGOSA via built-in 4G. Configure SRCS2000 UTM Zone 37N in ApekSurv. Load SAGEOID17 geoid. Verify on SGS control before commencing. AR stakeout for column grid layout. 120° IMU for tilt-compensated recording on uneven construction ground. As-staked QA report exported from ApekSurv at end of session.
SCENARIO 2 — NEOM DESERT CORRIDOR (NO NGOSA):
MAX5 base station on established project control monument at corridor entry. 5W LoRa covers 25 km along the flat desert corridor. Two AP20 AR rover teams work independently, both receiving corrections from the same MAX5. Full Fixed RTK throughout the corridor. Session length limited by MAX5 battery (8+ hours). No cellular data required.
SCENARIO 3 — PIPELINE ROUTE SURVEY (MIXED COVERAGE):
AP40 Laser+ rover + MAX5 base leap-frogged along the corridor. Where NGOSA coverage exists, connect via NTRIP. Where it fails (baseline >70 km), switch to MAX5 base on nearest SGS control. Laser used to measure pipeline crossing positions across wadis and road crossings without entering hazardous areas. Single operator covers both GNSS and laser offset measurement in one session.
FAQ
What coordinate system does Saudi Arabia use for GNSS survey?
Saudi Arabia's national coordinate system is SRCS2000 (Saudi Reference Coordinate System 2000), based on the ITRF2000 reference frame at epoch 2000.0 using the GRS80 ellipsoid. The projection is UTM — Zone 36N for western Saudi Arabia, Zone 37N for central Saudi Arabia (including Riyadh), and Zone 38N for the Eastern Province. For height, apply the SAGEOID17 geoid model to convert GPS ellipsoidal heights to orthometric (above mean sea level) heights. Legacy surveys may use Ain El Abd 1970 (AEA70), which requires a 7-parameter Helmert transformation to convert to SRCS2000.
How do I connect to NGOSA CORS in Saudi Arabia?
Register with NCSI (National Center for Spatial Information) to obtain NTRIP credentials for the NGOSA network. Configure the caster address, port, mountpoint, username, and password in ApekSurv under Communication → NTRIP. Select RTCM 3.x format. NGOSA supports standard NTRIP v1 and v2 protocols compatible with all APEKS receivers. Coverage is strongest in Riyadh, Jeddah, and the Eastern Province. For remote or desert sites, verify baseline distance to the nearest NGOSA station before relying on NTRIP.
What do I do when NGOSA coverage is not available?
Deploy a base+rover configuration. Set up an AP10 or AP20 as a base station on a known SGS control point, broadcasting corrections via 2W UHF radio to the rover within 8–15 km. For larger project areas — pipeline corridors, remote desert infrastructure — use the MAX5 dedicated base station: 5W LoRa radio, 25 km range, 13,200 mAh battery for 8+ hours. No internet, no CORS subscription, no cellular required. RTK accuracy is identical to CORS-based RTK when the base is correctly set up on coordinated control.
Will Chinese GNSS receivers work in Saudi Arabia without firmware restrictions?
APEKS receivers use international firmware with no geo-fence restrictions. OTA firmware updates work from any internet connection, including Saudi Arabia, without requiring Chinese server access or VPN. Some Chinese GNSS brands ship firmware that restricts OTA updates to within China — verify this explicitly with any non-APEKS supplier before purchase, as firmware obsolescence over a multi-year project creates CORS compatibility issues.
How do I handle the difference between AEA70 and SRCS2000 on a mixed-datum project?
Do not mix AEA70 and SRCS2000 coordinates without applying a datum transformation. The horizontal shift between the two datums varies across Saudi Arabia — typically 5–30 metres depending on location. Obtain the project-specific 7-parameter Helmert transformation parameters from the project's geodetic consultant and load them into ApekSurv's coordinate system settings. Verify the transformation on a minimum of two independent control points before commencing production survey. If no transformation parameters are available, resurvey all control in SRCS2000 from published national geodetic monuments.
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RTK GNSS FOR SAUDI ARABIA. NO CORS REQUIRED.
APEKS receivers cover Vision 2030 infrastructure survey from Riyadh urban sites on NGOSA CORS to remote desert corridors with MAX5 base station at 25 km LoRa range. International firmware. No geo-fence. SRCS2000 ready.
View APEKS RTK Receivers →References
- NCSI — National Center for Spatial Information, Saudi Arabia (ncsi.gov.sa)
- SRCS2000 Technical Specifications — Saudi Geodetic Survey, 2000
- SAGEOID17 — Saudi Arabia Geoid Model, NCSI 2017
- ISO 17123-8:2015 — Field Procedures for GNSS RTK
- RTCM Standard 10403.3 — Differential GNSS Services
- APEKS MAX5 Base Station Datasheet, 2026
- Unicore Communications UM980 Product Brief