OSS-RTK – Open Survey System RTK

NTRIP Server

Overview

The device runs a lightweight NTRIP caster accessible over the WiFi Access Point. GNSS rover receivers connect to it to receive real-time RTCM corrections relayed from the LoRa link.

Network Setup

LoRa Transmitter                  OSS Receiver (this device)              GNSS Rover
    ╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶
                                  ┌──────────────────┐
    RTCM via LoRa ──────────────► │  WiFi AP         │ ◄─── Rover connects
                                  │  192.168.4.1     │      to WiFi
                                  │                  │
                                  │  NTRIP Caster    │
                                  │  Port 2101       │ ◄─── GET /LORA HTTP/1.1
                                  │  Mount: /LORA    │ ───► ICY 200 OK
                                  │                  │ ───► RTCM binary stream
                                  └──────────────────┘

Connection Details

Parameter Value
WiFi SSID OSS-LoRa-RX
WiFi Password lora123456
Server IP 192.168.4.1
NTRIP Port 2101
Mount Point LORA
Max Clients 4 simultaneous

NTRIP Protocol Flow

1. Source Table Request

Client sends:

GET / HTTP/1.1

Server responds:

SOURCETABLE 200 OK
Content-Type: gnss/sourcetable

STR;LORA;LORA;RTCM 3.x;1005,1077,1087,1097,1127,1230;2;GPS+GLO+GAL+BDS;SNIP;ESP32;N;N;560;none
ENDSOURCETABLE

Connection is closed after sending the source table.

2. Mount Point Stream Request

Client sends:

GET /LORA HTTP/1.1

Server responds:

ICY 200 OK
Content-Type: gnss/data

<binary RTCM data stream>

The connection stays open. Complete RTCM frames are pushed to the client as they arrive from the LoRa link.

Client Lifecycle

New TCP connection on port 2101
        │
        ▼
  Assign to free client slot (max 4)
        │
  No free slot? → 503 Service Unavailable → close
        │
        ▼
  Wait for GET request
        │
        ├── GET /LORA → ICY 200 OK → authenticated = true → stream RTCM
        │
        └── GET / HTTP → send source table → close
        │
        ▼
  Stream active (broadcastRTCMData pushes frames)
        │
        ▼
  Client disconnects → slot freed

Rover Configuration

Configure your GNSS rover’s NTRIP client with:

Setting Value
Host / IP 192.168.4.1
Port 2101
Mount Point LORA
User / Password (not required)

Example: u-blox u-center

  1. Connect rover to OSS-LoRa-RX WiFi
  2. Receiver → NTRIP Client
  3. Address: 192.168.4.1:2101
  4. Mount point: LORA

Example: SW Maps (Android)

  1. Connect phone to OSS-LoRa-RX WiFi
  2. NTRIP Connection → Add
  3. Host: 192.168.4.1, Port: 2101, Mount: LORA

OLED Display

The display shows live statistics updated every 500ms:

┌────────────────────────────┐
│ OSS RTCM RX         [███ ]=│
│────────────────────────────│
│ RX:          2.3/s (1s)    │
│ Err:              0.5%     │
│ WiFi:             1/4      │
│ NTRIP:            1/4      │
└────────────────────────────┘
Line Meaning
RX RTCM message rate (msg/s) and seconds since last message
Err Error rate (timeouts + CRC failures as % of total)
WiFi Connected WiFi stations / max
NTRIP Authenticated NTRIP clients / max

The battery icon in the header has 4 segments (one per started 25 %); one segment blinks below 10 %. See configuration.md → Battery Monitoring.

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