- Change google earth pro for mac scale to meters how to#
- Change google earth pro for mac scale to meters 32 bit#
- Change google earth pro for mac scale to meters full#
- Change google earth pro for mac scale to meters code#
Optional ByVal unit As Char = "M"c) As Doubleĭim dist As Double = Math.Sin(deg2rad(lat1)) * Math.Sin(deg2rad(lat2)) + _ Public Function distance(ByVal lat1 As Double, ByVal lon1 As Double, _īyVal lat2 As Double, ByVal lon2 As Double, _ The wikipedia entry states that the distance calcs are within 0.6m for 100km longitudinally and 1cm for 100km latitudinally but I have not verified this as anywhere near that accuracy is fine for my use. LatMid = (Lat1+Lat2 )/2.0 // or just use Lat1 for slightly less accurate estimate double latMid, m_per_deg_lat, m_per_deg_lon, deltaLat, deltaLon,dist_m
Change google earth pro for mac scale to meters code#
In the code below I've left the raw numbers to show their relation to the formula from wikipedia. The displayed Map is characterized by its own pixel width.For approximating short distances between two coordinates I used formulas from
Check it against any to the tables posted here and the numbers will match.īased on all the info provided, I have built a function that gives the best z applied to a map when you want to have a horizontal line that represents N% of the displayed Map. I have used this hundred of time and overlaying it with actually field survey data and its always been correct. If you want feet divide that 0.3048Īs for sources I essencial reversed engineer about 5 years ago from various bit of info and documentation I found on the web including Google and MS mapping support sites. If you screen capture a 1000 x 1000 pixel image of that area the dimension are 105.56 meters square. That is the length and height of one pixel from an image at latitude 45 at zoom level 20. Now lets say our image is at latitude 45. Lets say I have an image at zoom level 20 (as zoomed as they currently let you get) Take 0.009330692 (Zoom 24 at equator) double it for zoom 23, again for zoom 22, again for zoom 21 and one last time for zoom 20.
Change google earth pro for mac scale to meters how to#
Now for an example of how to use the above data. Why this is level 24 was chosen I don't know however as someone else here worked out 0 gets you down to one 256 pixel tile for the earth.
Change google earth pro for mac scale to meters 32 bit#
32 bit integers are also efficient to store and process. This is a logical choice as it yields global accuracy to about one centimeter which is plenty for aerial imagery.
Change google earth pro for mac scale to meters full#
They then took that and divided it by a full 32 bit integer. (note in a previous post someone used a value of 40,075,160 I've seen this in Wikipedia a few places and it's incorrect. So back 15-20 year ago someone took WGS-84 as base data. What you need for these images to be used with any accuracy is to know the dimension of each pixel then scale the image according to whatever your overlaying it with.
Scale ratios are relative to printed documents not computer screens. Well its not really a legitimate question to start with. Unit at Latitude = (Cosine of Latitude) X (Unit at Equator) Zoom level 24 uses 2 to the 32 power (4,294,967,296) pixels at circumference.Įquatorial Circumference / 2 32 =. for zoom level N, the scale is one half of that of zoom level N-1.for zoom level 1, the scale is one half of that of zoom level 0.so the point is that the scale depends on your monitor's PPI and on the latitude (because of the Mercator projection).You cannot observe this in Google Maps since it automatically moves to the zoom level 1, but you can see it on OpenStreetMap's map (it uses the same tiling scheme).ģ60 degress on the Equator are equal to Earth's circumference, 40,075.16 km, which is 40075160 mĭivide 40075160 m with 0.065 m and you'll get 616313361, which is a scale of zoom level 0 on the Equator for a computer monitor with 100 DPI On zoom level 0, the whole 360 degrees of longitude are visible in a single tile. That means 256 pixels are roughly 6.5 cm of length. Let's say your computer monitor has 100 pixels per inch (PPI). Google's web map tile has 256 pixels of width.To help you understand the maths (not a precise calculation, it's just for illustration):
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