Ahhhhhhh now the days of using Google Earth to determine dimensions of structures etc. are over. At long last I found a GIS server for the part of Switzerland I model.
There is one handycap, the info is up to date i.e. not back in 1969-75, but that’s not a large problem.
BTW I have a sneaky suspicion that these GIS maps are available for anything in NA, too. It’s just a matter of finding them.
Interesting find HJ. Having done GIS and arieal photo interpretation work in a previous life…
The problem is, with any GIS, what data sets are put into them. A GIS is not a true map per se. It is a Geographical Informational System. Basically layers of data that can be moved in and out of the base maps.
So if you start with say, USGS topo maps and add to that arieal photo data, it is a good start. But then the database of specifics has to be built, in the case I worked on, locating and cataloging data on USTs (underground storage tanks).
And then, the UST data could be used for several things, EPA water pollution info, fire protection, insurance/property transfer/Phase I work, etc.
So…
If the structure data set is from 1967-75, it will remain that way until someone finds a need to update it for whatever (property tax, fire insurance, environmental imnpact, etc.) reasons. Or if the data is completely un-needed, then good luck in getting that dataset updated.
Garrett,
I never looked into how they do it, I just use the stuff they provide. Like being able to determine what coverage a certain area has is of no interest, but using the same feature to determine the linear dimensions of structures beats the Google Earth methods by a bit… The scale gets down to 0.1m (4") and if I use the crosshair cursor it’s accurate enough for 1:22.5 structures. 
True. I have used Google Earth to hunt down some abandoned railways in Germany, Austria and the Czech Republic. Fun stuff.
Nice to have a way to measure dimensions, in the old days (college tests) we were given an areal photo and told to determine the RF. You hoped to God there was something (ball diamond, standard interstate lane, football field, etc.) that you could use to at least get close to pegging a scale!
I have found Google satellite pics to be of great interest. One of my interests are the railroads in Colorado and neighboring States. I have followed the lines out from Denver along the Moffat Sub and on wards to Ogden and SLC.
The other direction took me from Ogden to North Platte and some parts of NE.
There is so much to be seen and I have been able to view the Townships in States where I have friends (yep, I do have one or two Lol)
There are web sites which put meat on the flesh of the views such as the wonderful
http://www.coloradorailfan.com/
which shows the locos, freight and present day Amtrack trains on some of the lines.
Admittedly my little railroad in not based in the present day but some 40-50 years ago even so many structures, tunnel portals and so forth are unchanged since those days. Even some older type signaling equipment is still around. The only drawback is that so much of the old MILW road can no longer be seen.
Alan Lott said:You, too. :lol: :lol: I have carefully selected friends all over the place, amongst other things, it sure helps when one is looking for accurate info.
There is so much to be seen and I have been able to view the Townships in States where I have friends [b](yep, I do have one or two Lol)[/b]
Garrett said:
True. I have used Google Earth to hunt down some abandoned railways in Germany, Austria and the Czech Republic. Fun stuff.Nice to have a way to measure dimensions, in the old days (college tests) we were given an areal photo and told to determine the RF. You hoped to God there was something (ball diamond, standard interstate lane, football field, etc.) that you could use to at least get close to pegging a scale!
The sortie/mission details included the flying height and the focal length of the lens taking the image.
Simply divide the focal length in feet into the flying height and you had the general scale - for vertical images anyhow.
Example - flying height - 10,000 ft and focal length of lens 12" = scale = 1/10,000…
tac
www.ovgrs.org
Terry A de C Foley said:Garrett said:
True. I have used Google Earth to hunt down some abandoned railways in Germany, Austria and the Czech Republic. Fun stuff.Nice to have a way to measure dimensions, in the old days (college tests) we were given an areal photo and told to determine the RF. You hoped to God there was something (ball diamond, standard interstate lane, football field, etc.) that you could use to at least get close to pegging a scale!
This is where the old RAF aerial photography had the edge on everybody else’s.The sortie/mission details included the flying height and the focal length of the lens taking the image.
Simply divide the focal length in feet into the flying height and you had the general scale - for vertical images anyhow.
Example - flying height - 10,000 ft and focal length of lens 12" = scale = 1/10,000…
tac
www.ovgrs.org
GIS mapping has been available in NA for at least 5 years now. I am not sure if the website is open to the public though. I used to use GIS maps in my past life as a building inspector/zoning officer.
A couple seconds on The Google turned this up:
http://www.nashville.gov/mpc/property/
One of the oldest GIS type maps I ever saw dated to 1970. It was Battelle’s voter/census map for Columbus, “The city of broken glass” Ohio.
Garrett said:Terry A de C Foley said:Garrett said:
True. I have used Google Earth to hunt down some abandoned railways in Germany, Austria and the Czech Republic. Fun stuff.Nice to have a way to measure dimensions, in the old days (college tests) we were given an areal photo and told to determine the RF. You hoped to God there was something (ball diamond, standard interstate lane, football field, etc.) that you could use to at least get close to pegging a scale!
This is where the old RAF aerial photography had the edge on everybody else’s.The sortie/mission details included the flying height and the focal length of the lens taking the image.
Simply divide the focal length in feet into the flying height and you had the general scale - for vertical images anyhow.
Example - flying height - 10,000 ft and focal length of lens 12" = scale = 1/10,000…
tac
www.ovgrs.org
NOW someone tells me such things!
The RFC/RAF has been doing it this way since 1911, using the principals determined by the then-Captain of Engineers Dr Hugh Hamshaw-Thomas [later Wg Cdr] - father of imagery aerial photography as far as the British are concerned.
Hamshaw Thomas pioneered the use of ground and aerial photography for intelligence purposes, firstly as an Royal engineer surveyor working on behalf of the Royal Artillery in Palestine in 1916, then latterly in the Royal Flying Corps, serving in France for the remainder of WWI. The Medmenham Collection boasts many of Dr Hamshaw-Thomas’s original manuals and photographs, and his prototype of the “Type D” Stereoscope, familiar to many who have undergone an “Air Photo Reading” course. Dr Hamshaw Thomas returned to service as a Wing Commander during WWII and was instrumental in training many of those who served at RAF Medmenham. You can see much of this remarkable collection at Chicksands in Bedfordshire UK. B
By appointment, of course, otherwise you’ll get shot dead, or eaten alive - it’s also the home of the British Army’s Intelligence Corps.
So having established that scaling and measuring on vertical imagery is hardly a state secret, there are THREE methods of establishing dimensions of any object on VERTICAL imagery.
The focal length/height method I just showed you.
The known object method you mentioned.
and 3. The photo/map comparison method, where you identify three points on the map and the same three points on the image, and compare them mathematically. Basically another form of the known object method.
I thought everybody knew that. In our house it’s common knowledge…
tac
www.ovgrs.org
tac’s post prompts me to ask a question I have been attempting to get answered for some time.
While in the service, I was instructed on a method of determining range (distance) of a target (object) by extending my arm and holding up 1,2,3 or 4 fingers against a building, man or vehicle, then by determining an estimated known height, one can estimate the range of the target.
I hope I am explaining this well enough. Does anyone know how the calculation is done?
Hmmm, racking my brains here, but here goes - I’m sure that if I’m wrong, the gunners here will shoot me down -
Holding your hand outstretched from the shoulder -
Outspread hand = 300 mils
Clenched fist = 180 mils
All four fingers = 125 mils
Three fingers = 100 mils
Two fingers = 70 mils
One finger = 30 mils
To calculate distance to target of known size - 1000/36 x objects size in inches/mils
To calculate size of target at known distance - Object size in inches = 36/1000 x Distance in yards x mils
So spoges my snipers notes.
I use a laser, me.
tac
www.ovgrs.org
Your formula seems to work out.
I was given this info back as an Army tank crewman as a backup if we lost our analog rangefinder. I’ve often wanted to use this but forgot the mils. Maybe my golf game will improve now.
THANKS!