# Select Geo Data

This is a list of files containing GPS data points that can be displayed and investigated with the Display Geo Data App or displayed below as the raw data. Some data points (mostly flights) were collected with GPS trackers, other data points were collected using proffessional grade GPS devices using Differential GPS methods down to cm accuracy. See Discussion: Select Geo Data for how the data was gathered.

## Data File List

Click one of the following File Names to show the data visually in the Geo Data App. Scroll down in the App to see all the coordinates. Click a point to see additional calculated values for any data point.

## Selected Data File

Click on show data right of a filename in the Data File List to load the raw data into the text fields below. You can then copy the text ans save it in a file on your computer for further processing.

Data File Name: ⇐ Select another file

If you know the password you can Upload Geo Data.

## Data Format

The data specifies for each data point an ID, ECEF X,Y,Z coordinates, a description and optionally an EGM96 Elevation in this order. The values must be separated by a comma. You can import the data from spreadsheets that are saved in CSV format.

Optionally you can specify some Parameters for the Geo Data App that are passed to the Geo Data App to show a certain view.

$Parameter = value : ID, X, Y, Z, Description, Elevation :  Note: Elevation is Optional in this format. You can specify a common Geoid Height in the Geo Data App that is then used to calculate a common elevation for all data points. You can pass a corresponding value to the App by defining it as a Parameter: $SurfaceElevation = 336.879
$GeoidHeight = -31.02 : ID, X, Y, Z, Description :  If you don't have any description but elevation data, you can skip the Description and place the elevation data in that column, but then you have to include$TextIsElevation = true at the first line!

$TextIsElevation = true$Parameter = value
:
ID, X, Y, Z, Elevation
:



Note: After displaying a Geo Data File in the Geo Data App you can save changes in the settings made there. The same settings made in the Data File here have priority over the saved paramaeters of the Geo Data App. So only use parameters here that are essential, like TextIsElevation. All display settings are better saved in the App.

ECEF: (Earth Centered, Earth Fixed) is an orthogonal coordinate system, that has the origin on the mass center of the earth, X axes pointing to the 0-meridian, X/Y plane in the equatorial plane, Y axes pointing to east longitude 90° and Z axis pointing to the north pole. The coordinates are expressed in meters.

NGS: GPS measurements give earth-centered coordinates (ECEF), usually displayed as height above the reference ellipsoid, which cannot be related accurately to orthometric height above the geoid without accurate gravity data for that location. In the US, NGS has undertaken the GRAV-D ten-year program to obtain such data with a goal of releasing a new definition in 2022.

EGM96: (Earth Gravitational Model 1996) is a geopotential model of the Earth consisting of spherical harmonic coefficients complete to degree and order 360. The EGM96 model defined the Geoid heights for the whole world.

Elevation: The elevation here is the height of a data point above or below the reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface (see Geodetic datum § Vertical datum).

## Parameters for the Geo Data App

You can specify the following Parameters to transfer some values to the Geo Data App. They must be inserted exactly as specified at the beginning of the CSV data list. You can generate a list of Parameters in the Geo Data App by clicking the button Get App Parameters in the Parameters panel. Here is an example:

$DataSourceLink = 'https:\\host.dom\..'$DataSourceName = 'Source Name'
$TextIsElevation = true$SurfaceElevation = 336.879
$GeoidHeight = -31.02$CameraZoom = 133
$CameraPos = [ -14993.144, -5527239.597, 3172141.455 ]$CameraUp = [ -0.0014846509300273785, -0.8631876539997818, 0.5048810451918045 ]
$CameraViewCenter = [ -11903.600251313444, -5517422.508645069, 3188934.670829643 ]$ViewCenterMode = 1
$SkipPoints = 3$FirstPointIx = 0
$LastPointIx = 6528$SelRefPoint = 5451
$SelPoint1 = -1$SelPoint2 = -1
$PointSymbolSize = 4$ConnectPoints = false
$DrawGround = false$DrawHeights = false
$DrawCoordSys = false$DrawInfos = false
$DrawCompass = true$AngleFormat = 0
$LatLongFormat = 1$GroundSize = 100
$Image = "2019-01-21-Lake-Ponchartrain-no-refraction.jpg"$ImageX = 0
$ImageY = 0$ImageScale = 1.2
$ImageAlpha = 1  Note:$TextIsElevation = true must only be used if no text/description is used in the data and the text column contains elevation data. If used, it must be on the first line.

This parameters are used as the initial view settings in the Geo Data App. You can reset the view to this initial state by clicking the Reset-View button (1) at the bottom right of the display. For any not specified values, a corresponding default is calculated from the point corrdinates.