GeoPressureAPI

Overview

GeoPressureAPI is a JSON API that enables computation of pressure mismatch between geolocator pressure timeseries and atmospheric pressure from ERA5-LAND reanalysis data.

This documentation describes how to use the GeoPressure API. Please file an issue if you find anything missing.

Available Endpoints

The GeoPressure API provides four main endpoints:

Endpoint	Description
Pressure Map	Compute pressure mismatch maps from geolocator data
Pressure Timeseries	Extract pressure timeseries at specific locations
Ground Elevation Path	Get elevation profiles along polylines
Pressure Data Path	Extract atmospheric variables along paths

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1. Pressure Map

Endpoint: POST /glp.mgravey.com/GeoPressure/v2/map/

Overview

Compute maps of pressure mismatch from geolocator pressure timeseries. Returns GeoTIFF maps with pressure mismatch analysis.

Features

• MSE Layer: Mean Square Error between geolocator and ERA5 pressure data (with mean error removed for altitude flexibility)
• Mask Layer (optional): Proportion of timeseries within ground elevation range using barometric formula and SRTM data
• Optimization: Use maskThreshold to filter pixels and reduce computation time
• Data Source: ERA5-Land (1981 to 3 months from real-time), 1-hour resolution

Output Layers

1. MSE: Pressure mismatch computed using Mean Square Error
2. Mask: Altitude feasibility based on barometric formula and SRTM-90 elevation data

Request Parameters

Parameter	Type	Required	Default	Description
W	number	✅		West coordinate (-180° to 180°)
S	number	✅		South coordinate (-90° to 90°)
E	number	✅		East coordinate (-180° to 180°)
N	number	✅		North coordinate (-90° to 90°)
pressure	number[]	✅		Atmospheric pressure values (Pascal)
time	number[]	✅		UNIX timestamps (seconds since 1970-01-01)
label	(string|number)[]	✅		Grouping labels for pressure data
scale	number		10	Pixels per degree (10 = 0.1°/~10km, 4 = 0.25°/~30km)
maxSample	number		250	Maximum datapoints for computation (randomly sampled)
margin	number		30	Altitude error margin in meters (1hPa ≈ 10m)
includeMask	boolean		true	Include mask layer in output
maskThreshold	number		0	Filter pixels by mask value (0-1, e.g., 0.9 for 90%+ feasibility)

Response Format

Field	Type	Description
status	string	"success" or "error"
taskID	number	Unique task identifier
labels	(string|number)[]	Unique labels in same order as URLs
urls	string[]	Download URLs for GeoTIFF files
resolution	number	Map resolution in degrees
size	number[]	Map dimensions [width, height]
bbox	object	Bounding box coordinates
includeMask	boolean	Whether mask layer is included
maskThreshold	number	Applied mask threshold
errorMessage	string	Error description (if status = "error")
advice	string	Troubleshooting guidance (if status = "error")

GeoTIFF Content

Each URL returns a GeoTIFF file with:

• Band 1: MSE values
• Band 2: Mask values (if includeMask = true)

Special values:

• -2: Water/no data areas
• -1: Pixels below mask threshold

Example Usage

POST /glp.mgravey.com/GeoPressure/v2/map/
Content-Type: application/json

{
  "W": -18,
  "S": 4,
  "E": 16,
  "N": 51,
  "time": [1572075000, 1572076800, 1572078600],
  "pressure": [97766, 97800, 97833],
  "label": [1, 1, 1]
}

Response:

{
  "status": "success",
  "taskID": 1639259414,
  "data": {
    "labels": [1],
    "urls": ["https://earthengine.googleapis.com/v1alpha/..."],
    "resolution": 0.25,
    "size": [136, 188],
    "bbox": { "W": -18, "S": 4, "E": 16, "N": 51 },
    "time2GetUrls": 11.61,
    "includeMask": true,
    "maskThreshold": 0.9
  }
}

---

2. Pressure Timeseries

Endpoint: POST /glp.mgravey.com/GeoPressure/v2/timeseries/

Overview

Extract pressure timeseries at a specific location, with optional altitude computation when geolocator pressure data is provided.

Features

• Pressure extraction at precise coordinates
• Altitude computation using barometric formula (when pressure provided)
• Land fallback: Automatically moves water coordinates to nearest land
• Flexible time ranges: Use time arrays or start/end timestamps

Request Parameters

Parameter	Type	Required	Description
lon	number	✅	Longitude coordinate (-180° to 180°)
lat	number	✅	Latitude coordinate (-90° to 90°)
pressure	number[]	⚠️*	Geolocator pressure values (Pascal)
time	number[]	⚠️*	UNIX timestamps (required if pressure provided)
startTime	number	⚠️**	Start timestamp (required if no pressure)
endTime	number	⚠️**	End timestamp (required if no pressure)

* Required together
** Required if pressure not provided

Response Format

Field	Type	Description
status	string	"success" or "error"
taskID	number	Unique task identifier
url	string	CSV download URL
distInter	number	Distance to nearest land (meters, if moved from water)
lon	number	Actual longitude used
lat	number	Actual latitude used

CSV Output Format

Column	Description
time	UNIX timestamps
pressure	ERA5 pressure values
altitude	Computed altitude (only if geolocator pressure provided)

Example Usage

POST /glp.mgravey.com/GeoPressure/v2/timeseries/
Content-Type: application/json

{
  "lon": 6,
  "lat": 46,
  "startTime": 1497916800,
  "endTime": 1500667800
}

Response:

{
  "status": "success",
  "taskID": 1639259414,
  "data": {
    "url": "https://earthengine.googleapis.com/v1alpha/...",
    "format": "csv"
  }
}

---

3. Ground Elevation Along a Path

Endpoint: POST /glp.mgravey.com/GeoPressure/v2/elevationPath/

Overview

Extract ground elevation statistics from SRTM-90 data along a polyline path.

Request Parameters

Parameter	Type	Required	Default	Description
lon	number[]	✅		Longitude coordinates (-180° to 180°)
lat	number[]	✅		Latitude coordinates (-90° to 90°)
scale	number	✅		Elevation data resolution (pixels per degree)
samplingScale	number	✅		Path sampling resolution (pixels per degree)
percentile	number[]		[10, 50, 90]	Elevation percentiles to compute (0-100)

Response Format

Field	Type	Description
status	string	"success" or "error"
taskID	number	Unique task identifier
percentileData	object	Elevation statistics and path information
scale	number	Elevation data scale (meters per pixel)
samplingScale	number	Path sampling scale (meters per pixel)
percentile	number[]	Computed percentiles

Percentile Data Object

Array	Description
"10", "50", "90"	Elevation values for each percentile
distance	Cumulative distance along path (meters)
lat, lon	Resampled coordinates
stapId	Step position along path

Example Usage

POST /glp.mgravey.com/GeoPressure/v2/elevationPath/
Content-Type: application/json

{
  "lon": [8.47, 9.41, 9.01, -0.91, 14.24, 27.30, 34.39, 30.00],
  "lat": [48.89, 44.78, 40.07, 37.68, 17.33, 7.32, 8.09, -23.13],
  "scale": 10,
  "samplingScale": 1,
  "percentile": [10, 50, 90]
}

Response:

{
  "status": "success",
  "taskID": 1639259414,
  "data": {
    "percentileData": {
      "10": [0, 0, 0, 305, 357, 289, 426, 399],
      "50": [237, 237, 587, 552, 551, 363, 569, 553],
      "90": [880, 880, 1260, 1138, 859, 480, 900, 756],
      "distance": [0, 462486, 986718, 1886940, 2997968],
      "lat": [44.927, 44.927, 34.943, 24.959, 14.976],
      "lon": [4.992, 4.992, -4.992, 4.992, 14.976],
      "stapId": [0, 1, 2, 3, 4]
    },
    "scale": 1111390.0,
    "samplingScale": 1111390.0,
    "percentile": [10, 50, 90]
  }
}

---

4. Pressure Data Along a Path

Endpoint: POST /glp.mgravey.com/GeoPressure/v2/pressurePath/

Overview

Extract atmospheric variables from ERA5/ERA5-LAND data along a path with optional altitude computation from geolocator pressure data.

Features

• Multi-variable extraction: Any ERA5 atmospheric variables
• Dataset options: ERA5-LAND, ERA5 single-levels, or combined
• Altitude computation: When geolocator pressure provided
• Parallel processing: Configurable workers for large datasets

Request Parameters

Parameter	Type	Required	Default	Description
lon	number[]	✅		Longitude coordinates (-180° to 180°)
lat	number[]	✅		Latitude coordinates (-90° to 90°)
time	number[]	✅		UNIX timestamps (must match coordinate array length)
variable	string[]	✅		ERA5 variable names
pressure	number[]			Geolocator pressure (Pascal, enables altitude computation)
dataset	string		"both"	Data source: "land", "single-levels", or "both"
workers	number		10	Parallel processing chunks

Response Format

Field	Type	Description
status	string	"success" or "error"
taskID	number	Unique task identifier
data	object	Variable arrays (see below)

Data Object Arrays

Array	Description
time	UNIX timestamps (closest ERA5 match)
altitude	Computed altitudes (if pressure provided)
{variable}	One array per requested variable

Example Usage

POST /glp.mgravey.com/GeoPressure/v2/pressurePath/
Content-Type: application/json

{
  "lon": [17.5, 17.5, 17.5, 41.6, 41.6],
  "lat": [48.5, 48.5, 48.5, 41.6, 41.6],
  "time": [1501113600, 1501115400, 1501117200, 1501745400, 1501747200],
  "variable": ["surface_pressure", "temperature_2m"],
  "dataset": "land",
  "pressure": [98900, 99200, 99400, 100000, 100100],
  "workers": 1
}

Response:

{
  "status": "success",
  "taskID": 1639259414,
  "data": {
    "time": [1501113600, 1501115400, 1501117200, 1501745400, 1501747200],
    "altitude": [1234.5, 1245.2, 1256.8, 1290.7, 1301.2],
    "surface_pressure": [98765, 98823, 98881, 99055, 99113],
    "temperature_2m": [285.4, 286.1, 286.8, 288.9, 289.6]
  }
}

---

Installation

Server Setup

1. Clone repository

   git clone https://github.com/Rafnuss/GeoPressureAPI

2. Add authentication

   • Place Google Earth Engine service account JSON key in repository

3. Configure server

   • Update bootServer.sh with service address
   • Create logs directory

4. Network routing (if needed)

   sudo iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 80
   sudo iptables -t nat -A PREROUTING -p tcp --dport 443 -j REDIRECT --to-port 443

5. Start server

   bash bootServer.sh

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Data Sources & Limitations

• ERA5-LAND: 1981 to ~3 months from real-time
• Time resolution: 1 hour (use closest match for any timestamp)
• Spatial coverage: Global land areas
• Coordinate systems: WGS84 (EPSG:4326)

For more information, see:

• ERA5-LAND documentation
• Google Earth Engine ERA5 dataset