How to batch edit a field in a jpg EXIF header?

Question

I am busy with some drone mapping. However, the altitude value in the images are very inconsistent between repeating flight missions (up to 120m). The program I use to stitch my drone images into a orthomosaic thinks the drone is flying underground as the image altitude is lower than the actual ground elevation.

To rectify this issue, I want to batch edit the altitude values of all my images by adding the difference between actual ground elevation and the drone altitude directly into the EXIF of the images.

e.g. Original image altitude = 250m. Edited image altitude = 250m+x

I have found the exiftoolr R packages which allows you to read and write EXIF data through using the standalone ExifTool and Perl programs (see here: https://github.com/JoshOBrien/exiftoolr)

This is my code so far:

library(exiftoolr)

#Object containing images in directory
image_files <-dir("D:/....../R/EXIF_Header_Editing/Imagery",full.names=TRUE)

#Reading info
exif_read(image_files, tags = c("filename", "AbsoluteAltitude")) #Only interested in "filename" and "AbsoluteAltitude"

#Saving to new variable
altitude<-list(exif_read(image_files, tags=c("filename","AbsoluteAltitude")))

This is how some of the output looks like:

       FileName AbsoluteAltitude
1  DJI_0331.JPG          +262.67
2  DJI_0332.JPG          +262.37
3  DJI_0333.JPG          +262.47
4  DJI_0334.JPG          +262.57
5  DJI_0335.JPG          +262.47
6  DJI_0336.JPG          +262.57
ext.

I know need to add x to every "AbsoluteAltitude" entry in the list, and then overwrite the existing image altitude value with this new adjusted altitude value, without editing any other important EXIF information.

Any ideas?

I have a program that allows me to batch edit EXIF Altitude, but this makes all the vales the same, and I need to keep the variation between the values.

Thanks in advance

Answer 1

Just a follow up from @StarGeek answer. I managed to figure out the R equivalent. Here is my solution:

    #Installing package from GitHub
    if(!require(devtools)) {install.packages("devtools")}
    devtools::install_github("JoshOBrien/exiftoolr",force = TRUE)
    #Installing/updating ExifTool program into exiftoolr directory
    exiftoolr::install_exiftool()
    #Loading packages
    library(exiftoolr)

    #Set working directory
    setwd("D:/..../R/EXIF_Header_Editing")

    #Object containing images
    image_files <- dir("D:/..../R/EXIF_Header_Editing/Imagery",full.names = TRUE)

    #Editing "GPSAltitude" by adding 500m to Altitude value
    exif_call(args = "-GPSAltitude+=500", path = image_files)

And when opening the .jpg properties, the adjusted Altitude shows.

Thanks StarGeek