Understanding the response

A successful request to the GET /v2/assistance endpoint returns a multipart/mixed response containing one part per requested GNSS system. Each part carries a binary LPP message with the assistance data for that constellation.

Response structure

The response uses the standard HTTP multipart format with a boundary separator. Each part includes its own headers and a binary body:

Content-Type: multipart/mixed; boundary=boundary

--boundary
Content-Type: application/octet-stream
X-Constellation: gps
Content-Length: 3100

<binary LPP message for GPS>
--boundary
Content-Type: application/octet-stream
X-Constellation: gal
Content-Length: 2900

<binary LPP message for Galileo>
--boundary--

Part headers

Each part in the multipart response includes the following headers:

Response headers

The overall HTTP response includes the following headers:

LPP message format

Each binary part contains an LPP message encoded using UPER (Unaligned Packed Encoding Rules). The root ASN.1 element depends on the lpp query parameter used in the request:

To decode the binary LPP messages, use an ASN.1 decoder generated from the LPP 18.3.0 schema. See LPP ASN.1 schema for the schema file and supported data elements.

Handling partially unavailable data

If assistance data for a particular GNSS system is temporarily unavailable, the corresponding part still appears in the response but with the following differences:

• The X-GNSS-Error header is set (for example, currentlyNotAvailable).
• The binary body contains an LPP message where the A-GNSS-ProvideAssistanceData section includes only the gnss-Error field with a locationServerErrorCauses.cause value, such as undeliveredAssistanceDataIsSupportedButCurrentlyNotAvailableByServer.

Example of a response with partially unavailable data:

Content-Type: multipart/mixed; boundary=boundary

--boundary
Content-Type: application/octet-stream
X-Constellation: gps
Content-Length: 3100

<binary LPP message for GPS>
--boundary
Content-Type: application/octet-stream
X-Constellation: gal
Content-Length: 100
X-GNSS-Error: currentlyNotAvailable

<binary LPP message with gnss-Error for Galileo>
--boundary--

Related information

• Assistance data request
• LPP ASN.1 schema