GNSS Surveying in Indonesia: InaCORS Setup Guide 2026

Indonesia is the world's largest archipelago — 17,000 islands stretching 5,000 km from east to west, spanning three time zones, and hosting one of the fastest‑growing infrastructure pipelines in Southeast Asia. Road construction, plantation mapping, coastal monitoring, and mining surveys all depend on reliable GNSS positioning. The Badan Informasi Geospasial (BIG) operates the InaCORS network, which provides free NTRIP correction access to registered surveyors. Knowing how to configure InaCORS correctly, select the right coordinate system, and handle coverage gaps in outer islands is what determines whether a field team achieves centimetre‑level Fixed solutions or spends half the day troubleshooting. This guide covers everything needed to survey efficiently in Indonesia.

Indonesia GNSS Landscape: What Surveyors Need to Know

BIG (Badan Informasi Geospasial) is the national mapping authority that operates InaCORS. The network comprises more than 270 continuously operating reference stations distributed across the archipelago, with the densest coverage on Java and Sumatra — where most infrastructure projects are concentrated. Coverage on outer islands (Kalimantan interior, Papua highlands, Maluku, Nusa Tenggara Timur) is sparser; distances to the nearest station can exceed 100 km in some remote areas.

InaCORS Network — Coverage, Registration, and Access

Follow these four steps to get connected to InaCORS for your project.

Step 1 — Register for InaCORS access
Visit inacors.big.go.id and complete the online registration form. Provide your full name, organisation, intended use, and project area. BIG typically approves accounts within 1–3 business days. International project teams should register under their local partner company name. Keep login credentials secure — some NTRIP client configurations bind the account to a single device.

Step 2 — Check coverage for your project area
Use the InaCORS interactive map at inacors.big.go.id/peta to verify reference station locations near your project site. For Java, Bali, and Sumatra projects, expect a reference station within 30–50 km. For Kalimantan, Sulawesi, and Papua, gaps of 80–120 km are common in interior or highland areas — plan accordingly.

Step 3 — Download the mountpoint list
Connect to the InaCORS caster at cors.big.go.id port 2101 (no username/password required for the initial mountpoint list download). Review the mountpoint naming convention: stations are named by a four‑character BIG station code corresponding to city or district names. Select the mountpoint geographically nearest to your project site.

Step 4 — Verify network status before mobilising
InaCORS publishes real‑time network status at inacors.big.go.id. Before mobilising equipment to a remote site, confirm the nearest reference station is online. Unplanned maintenance outages occasionally affect individual stations — having the second‑nearest station as a backup mountpoint saves time in the field.

NTRIP Configuration for InaCORS in ApekSurv

APEKS receivers from AP20 onwards include a built‑in 4G modem. The receiver manages the InaCORS connection independently — no tethering to a mobile phone or data collector is required. This is particularly important for one‑person survey operations in plantation and road corridor environments where carrying a separate data collector adds logistical burden.

Indonesia Coordinate Systems — DGN95, TM‑3, and WGS84

Indonesia's national coordinate system is DGN95 (Datum Geodesi Nasional 1995), aligned to ITRF94 at epoch 1995.0. For practical field survey purposes, DGN95 and WGS84 are sufficiently aligned that most GNSS receivers treat them as equivalent. However, for legal cadastral surveys and government infrastructure projects, DGN95 must be stated explicitly in the survey report.

Indonesia uses the Transverse Mercator 3° belt system (TM‑3) for local grid coordinates. The country is divided into 7 TM‑3 zones. In ApekSurv, select the appropriate TM‑3 zone based on your project location. Using the wrong TM‑3 zone shifts all easting coordinates by hundreds of metres — verify zone selection before starting.

For orthometric heights (elevations above mean sea level), Indonesia uses the national vertical datum referenced to tide gauges. Apply the EGM2008 geoid model in ApekSurv for conversion from ellipsoidal to orthometric heights. For engineering projects requiring local vertical control, establish a benchmark from the nearest BPN vertical control monument.

Regional Coverage Gaps — When to Deploy a Local Base

Equipment Recommendations for Indonesian Field Conditions

Indonesia's equatorial climate presents specific challenges: ambient temperatures of 28–38°C, humidity above 85% for most of the year, frequent rain during the October–April wet season, and red laterite soil that infiltrates connectors if not sealed.

Minimum requirements for Indonesian field use:

• IP67 rating minimum (brief immersion protection) — IP68 preferred for river crossing surveys, coastal mapping, and wet season work.
• IK08 impact resistance — equipment is routinely transported by motorcycle, boat, and on foot through plantation access tracks.
• Operating temperature up to +60°C — receivers left in direct sunlight in the back of a pickup can exceed 50°C surface temperature.
• USB‑C or power bank charging — essential for remote sites without generator access.

APEKS model recommendations for Indonesia:

• AP30 Laser / AP40 Laser+ — best for plantation cadastral, road corridor, and infrastructure survey. Built‑in 4G for InaCORS, 120° IMU for slope survey under canopy, green laser for boundary peg measurements through vegetation.
• AP60 Vision — recommended for multi‑person survey teams and engineering projects where AR stakeout capability saves time on complex layouts.
• MAX5 Base Station — essential for Kalimantan, Papua, and Sulawesi remote projects. The 13,200 mAh battery survives a full shift without recharging, and the 5W LoRa covers plantation block perimeters reliably.

Practical Field Tips for Indonesia Survey

Quick Reference Table