Hello,
I have created a PS script that reads the GPS Latitude and Longitude from a JPG file.
In some cases, the GPS coordinates do not match with the picture's properties.
Function Get-EXIFDataFromJPGFile
{
<#
.NOTES
=============================================================================================================================================
Created with: Windows PowerShell ISE
Created on: 06-July-2020
Created by: Willem-Jan Vroom
Organization:
Functionname: Get-EXIFDataFromJPGFile
=============================================================================================================================================
.SYNOPSIS
This function reads the latitude and longitude data from a JPG file.
If no valid data is found, the return codes will be 1024 and 1024.
This code is based on
http://www.forensicexpedition.com/2017/08/03/imagemapper-a-powershell-metadata-and-geo-maping-tool-for-images/
#>
Param
(
[String] $FileName
)
$img = New-Object -TypeName system.drawing.bitmap -ArgumentList $FileName
$Encode = New-Object System.Text.ASCIIEncoding
$GPSInfo = $true
$GPSLat = ""
$GPSLon = ""
# =============================================================================================================================================
# Try to get the latitude (N or S) from the image.
# If not successfull then this information is not in the image
# and quit with the numbers 1024 and 1024.
# =============================================================================================================================================
Try
{
$LatNS = $Encode.GetString($img.GetPropertyItem(1).Value)
}
Catch
{
$GPSInfo = $False
}
If ($GPSInfo -eq $true)
{
[double]$LatDeg = (([Decimal][System.BitConverter]::ToInt32($img.GetPropertyItem(2).Value, 0)) / ([Decimal][System.BitConverter]::ToInt32($img.GetPropertyItem(2).Value, 4)))
[double]$LatMin = (([Decimal][System.BitConverter]::ToInt32($img.GetPropertyItem(2).Value, 8)) / ([Decimal][System.BitConverter]::ToInt32($img.GetPropertyItem(2).Value, 12)))
[double]$LatSec = (([Decimal][System.BitConverter]::ToInt32($img.GetPropertyItem(2).Value, 16)) / ([Decimal][System.BitConverter]::ToInt32($img.GetPropertyItem(2).Value, 20)))
$LonEW = $Encode.GetString($img.GetPropertyItem(3).Value)
[double]$LonDeg = (([Decimal][System.BitConverter]::ToInt32($img.GetPropertyItem(4).Value, 0)) / ([Decimal][System.BitConverter]::ToInt32($img.GetPropertyItem(4).Value, 4)))
[double]$LonMin = (([Decimal][System.BitConverter]::ToInt32($img.GetPropertyItem(4).Value, 8)) / ([Decimal][System.BitConverter]::ToInt32($img.GetPropertyItem(4).Value, 12)))
[double]$LonSec = (([Decimal][System.BitConverter]::ToInt32($img.GetPropertyItem(4).Value, 16)) / ([Decimal][System.BitConverter]::ToInt32($img.GetPropertyItem(4).Value, 20)))
#$GPSLat = $($LatDeg.ToString("###")) + "º "+$($LatMin.ToString("##"))+"' "+$($LatSec.ToString("##"))+ $([char]34) + " "+$LatNS
#$GPSLon = $($LonDeg.ToString("###")) + "º "+$($LonMin.ToString("##"))+"' "+$($LonSec.ToString("##"))+ $([char]34) + " "+$LonEW
$GPSLat = "$([int]$LatDeg)º $([int]$LatMin)' $([int]$LatSec)$([char]34) $LatNS"
$GPSLon = "$([int]$LonDeg)º $([int]$LonMin)' $([int]$LonSec)$([char]34) $LonEW"
Write-Verbose " The picture $FileName has the following GPS coordinates:"
Write-Verbose " $GPSLat"
Write-Verbose " $GPSLon"
# =============================================================================================================================================
# Convert the latitude and longitude to numbers that Google Maps recognizes.
# =============================================================================================================================================
$LatOrt = 0
$LonOrt = 0
If ($LatNS -eq 'S')
{
$LatOrt = "-"
}
If ($LonEW -eq 'W')
{
$LonOrt = "-"
}
$LatDec = ($LatDeg + ($LatMin/60) + ($LatSec/3600))
$LonDec = ($LonDeg + ($LonMin/60) + ($LonSec/3600))
$LatOrt = $LatOrt + $LatDec
$LonOrt = $LonOrt + $LonDec
# =============================================================================================================================================
# The numbers that where returned contained a decimal comma instead of a decimal point.
# So the en-US culture is forced to get the correct number notation.
# =============================================================================================================================================
$LatOrt = $LatOrt.ToString([cultureinfo]::GetCultureInfo('en-US'))
$LonOrt = $LonOrt.ToString([cultureinfo]::GetCultureInfo('en-US'))
Write-Verbose " The picture $FileName has the following decimal coordinates:"
Write-Verbose " $LatOrt"
Write-Verbose " $LonOrt"
}
else
{
# =============================================================================================================================================
# Ohoh... No GPS information in this picture.
# =============================================================================================================================================
Write-Verbose " The picture $FileName does not contain GPS information."
$LatOrt = "1024"
$LonOrt = "1024"
}
Return $LatOrt,$LonOrt,$GPSLat,$GPSLon
}
Add-Type -AssemblyName System.Drawing
Get-EXIFDataFromJPGFile "C:\TMP\WP_20170426_15_30_51_Pro.jpg"
The output is:
47º 33' -21" N
7º 35' -13" E
But if you check the picture's properties and check the coordinates, it says:
47;33;21.9
7;35;30.6
But.... there are also pictures where the output matches. EXIF version is in both cases the same.
So my question is: why does in some cases the EXIF information not match, thus the information from the function is not equal to the EXIF information the picture's properties.
With kind regards,
Willem-Jan
