Estimating the actual locations of the bridges in the photos can be relatively easy or quite difficult, if not impossible. Here are the steps I used to find the locations.
Photos with grid locations
Many of the photos include grid locations. Grid locations are usually in the form of a letter followed by a six-digit number. Photos 58 and 59, for example, have the grid location Q168224. Fortunately, there is a website that explains the grid locations used in World War II, and calculates the latitude and longitude for a given grid location. In this case, the grid location converts to 48.79613 N, 6.6039 E. Finding this point using Google Earth, it’s easy to see that there are no rivers or streams nearby. So the recorded grid location is probably not the actual bridge location. But doing a search in the area of the recorded grid location shows where the road crosses a small stream.
Note that the stream turns to the left immediately on the other side of the road. This is also the case for the stream in Photo 59:
Looking at this location relative to the recorded grid location, it is fairly close:
For this case, I have some confidence that the actual location of the bridge is at the point marked “Photo 58 Likely” given the proximity to the recorded grid location and the bend in the stream seen in the photo and on Google Earth. I point out these similarities for each of the bridge photo pages where possible, and give the latitude and longitude of my estimate for the photo location.
Photos with no grid location
For photos that do not have a grid location, but indicate a town or city, the first step is to look for modern road-river crossings. It is likely that many of the key roads now were also key roads during the war, with the exception of major expressways that bypass many cities. For example, Photos 15-20 do not provide a grid location, but are labeled as “Custines Meurthe.” Searching Google Earth for Custines, one sees only one bridge in the vicinity:
With Google Street View, we can see that the shape of the hills in the background is consistent with the background shown in Photo 17:
This makes the location seem plausible. One more clue helps to make the location seem very likely, and that is the building shown in the white box in Photo 19 below:
The bottom image is of what appears to be the same house, seen in Google Street View. The location of the modern bridge seen in the first view from above seems very likely to be the location of the bridge shown in Photos 15-20.