Part 1: Extracting exif data from photos using R
See the other parts in this series of blog posts.
My camera comes with an inbuilt GPS allowing you to geo-reference photos you take. Here is a simple example for how we can use this feature to create an interactive web map in R.
The photos come from a survey I did of oysters on a rocky shoreline. I took photos of each quadrat enabling me to geolocate the quadrats as well as record what occurred within them.
First get your hands on a few packages,
exif for extracting exif info in R,
dplyr for data management and
leaflet for making maps:
library(exifr) library(dplyr) library(leaflet)
Now set your working director the a folder that holds the photos in questions. We can then get the names of all the photos straight into R’s memory like this:
files <- list.files(pattern = "*.JPG") dat <- exifr(files)
pattern argument ensures we just grab the jpegs from the folder and nothing else.
Neat, we have our exif info as a dataframe. Now let’s select just the useful columns:
dat2 <- select(dat, SourceFile, DateTimeOriginal, GPSLongitude, GPSLatitude, GPSTimeStamp) write.csv(dat2, 'Exifdata.csv', row.names = F)
NB the select function comes from the
dplyr package. You can do this with base R too, but I prefer
dplyr. (You can get my dataframe here)
You can make a quick map of locations like this:
Make an interactive map
Interactive web maps are easy with the
leaflet package. We can plot the same points over and ESRI provided satellite image like this:
leaflet(dat2) %>% addProviderTiles("Esri.WorldImagery") %>% addMarkers(~ GPSLongitude, ~ GPSLatitude)
And here’s what it should look like:
Next up we will look at how to match these locations to the quadrat data I collected.