Google Earth - EBT's dot grid

Donald · Post by **Donald** » Wed Mar 15, 2006 9:33 pm

I like ernie's dot converter pretty much. I already used it last week to get me one more dot in the Netherlands. It showed me where I had to refuel during a business trip and it worked nicely.

I see at altitudes below 30 miles that the dots are not connected with their eastern and western neighbors - there is a gap in between. Is this a neccessary feature or can it be fixed?

There is also a small differerence between the edges of the spots and the grid lines - they do not coincide perfectly. To me it looks like bocky and you use slightly different sets of coordinates. It would be nice if we had one official set of dot coordinates for all google earth applications. Maybe avij can provide these figures.

ernie_hh · Post by **ernie_hh** » Thu Mar 16, 2006 3:09 pm

Donald wrote:I see at altitudes below 30 miles that the dots are not connected with their eastern and western neighbors - there is a gap in between. Is this a neccessary feature or can it be fixed?

That was a bug that made it from the preview version into the final. Should not happend. I fixed it now. Thanks for the reminder

Donald wrote:There is also a small differerence between the edges of the spots and the grid lines - they do not coincide perfectly. To me it looks like bocky and you use slightly different sets of coordinates. It would be nice if we had one official set of dot coordinates for all google earth applications. Maybe avij can provide these figures.

I noticed it already. I am not really sure if it is a problem in my dotmap or i the grid. Perhaps it is a problem in GoogleEarth. When i use the german grid my (eight) dots fit nearly perfectly in the grid. if i use the europe grid the fault is much bigger. Perhaps GoogleEarth is not able to paint vector graphics so accurate. I will compare my numbers to the grid if i have some extra time. Perhaps i can find a problem

greetings

Donald · Post by **Donald** » Thu Mar 16, 2006 8:29 pm

It looks much better now.

The north-south lines of the grids coincide with the dot borders. However, this is only so if the lines are centered. When I shift the lines to the left or right side of my screen, the lines separate from the dot borders. Also the lines of the German and the full map split up a little bit. The full map lines stay a little bit closer to the dot borders then.

The east-west grid lines coincide nicely with the dot corners but they shift a little bit north near the middle of a dot's side.

Dakkus · Post by **Dakkus** » Thu Mar 16, 2006 9:01 pm

Donald wrote:I like ernie's dot converter pretty much. I already used it last week to get me one more dot in the Netherlands. It showed me where I had to refuel during a business trip and it worked nicely.

I see at altitudes below 30 miles that the dots are not connected with their eastern and western neighbors - there is a gap in between. Is this a neccessary feature or can it be fixed?

There is also a small differerence between the edges of the spots and the grid lines - they do not coincide perfectly. To me it looks like bocky and you use slightly different sets of coordinates. It would be nice if we had one official set of dot coordinates for all google earth applications. Maybe avij can provide these figures.

Such official set already exists. ..at least to some extent.
We know the coordinates of one line intersection and also the intervals the dots have between each other. All other coordinates can quite easily be generated from that information.

Dakkus · Post by **Dakkus** » Thu Mar 16, 2006 10:54 pm

Well.. The dots' width is _always_ 0,44 degrees and their height is _always_ 0,28 degrees.
I didn't find any official information about the intersection coordinates, but according to my notes N 61.76, E 28.36 should be an exact, or practically equal to exact place of a corner of four dots. If I remember right, the information is from akiky who magically figured out the coordinates of some corner. (Or maybe he asked avij. I don't remember any more :/)

avij · Post by **avij** » Thu Mar 16, 2006 11:22 pm

Dakkus wrote:Well.. The dots' width is _always_ 0,44 degrees and their height is _always_ 0,28 degrees.

This is no longer true, the dot system was changed slightly about one year ago. See this message.

ernie_hh · Post by **ernie_hh** » Fri Mar 17, 2006 11:29 am

Thanks for providing the link (and of course all the data

)

This is what i calculate:

-12 + (0.42038216560509554140 * dotcol)

this give for a dot in col 52 a value:

9.85987261146497 (copied from my kml-file)

now i opend the german-grid an searched for the corresponding line and found:

9.859873

Now we need a mathematician to calculate how man miles differenz that is

I found the same with the other lines:

my value: 53.36
grid value: 53.360001 (always +0.000001 or -0.000001)

i know, thats a very small differenzes. But perhaps they are what we see?

perhaps i should make a go and build a testgrid with my numbers and see if it is a problem with GoogleEarth or with the rounding.

bucky:

did you generate your grids with a script or do you "paint" them right inside GE?

little hint: http://www.eurobilltracker.eu/index.php ... 2144;tab=9 <- many maps are also "dotmap"

avij · Post by **avij** » Fri Mar 17, 2006 12:14 pm

ernie_hh wrote:-12 + (0.42038216560509554140 * dotcol)
this give for a dot in col 52 a value:
9.85987261146497 (copied from my kml-file)

For reference, this is how I'd calculate the same, and how the grid is calculated in EBT. There is no 0.42038216560509554140 constant in EBT, only the starting and ending points and the number of grid cells are defined as in my previous message.

-12+(54+12)/157*52 = 9.85987261146496815280

Similarly, for a row 52 dot the longitude would be

29+(71-29)/150*52 = 43.56000

ernie_hh · Post by **ernie_hh** » Fri Mar 17, 2006 1:08 pm

avij:

thank you for the detailed information. i just changed my script to do the same

(didn't change something, but is cleaner code. the decimal places are limited by perl at this point)

one interessting point: you count from south to north, i count the otherway. perhaps i should change that too, some day

bocky · Post by **bocky** » Sat Mar 18, 2006 4:16 pm

ernie_hh wrote:bucky:

did you generate your grids with a script or do you "paint" them right inside GE?

Sorry about the late reply, I have been quite busy.

After I generated the full Europe grid I made a small program that lets me create a smaller grid (for the individual countries). I just enter the min and max longitude and latitude and the program analyses every line of the full .kml and writes to a new .kml the lines that are inside the rectangle.

I can make new files with 13 decimal places, that should make the grid as accurate as the dots.

Edit: I made a test file and the 53.36 coordinate you mentioned is being replaced by 53.3600006103516

When I manage to fix this I'll make new files, but I don't have much time to think about this right now

By the way, great job on the dot tool!

bocky · Post by **bocky** » Mon Mar 27, 2006 9:56 pm

I have updated the first post of this thread. The files are now available in 3 different formats and the coordinates have also been updated. Now they have 12 decimal places and should be as accurate as the dots.

Donald · Post by **Donald** » Mon Mar 27, 2006 10:27 pm

To me it looks fine now. Only at altitudes below 1000 ft there is a small discrepancy. Great job, bocky!

eddydevries · Post by **eddydevries** » Fri Jun 23, 2006 1:18 am

bocky wrote:I have updated the first post of this thread. The files are now available in 3 different formats and the coordinates have also been updated. Now they have 12 decimal places and should be as accurate as the dots.

I've tried to download the dot=borders.
But the links don't work at all ("The page cannot been displayed").

I would like to see where the borders of the dot are, because I'm going on hollidays to Germany and Austria this summer (ther are dotmaps avilable for Germany but not (yet) fot Austria).

bocky · Post by **bocky** » Fri Jun 23, 2006 1:45 am

eddydevries wrote:I've tried to download the dot=borders.
But the links don't work at all ("The page cannot been displayed").

They are working for me now, are you still unable to download the files? Maybe the server was down for a few moments.

eddydevries · Post by **eddydevries** » Fri Jun 23, 2006 8:03 am

I'm sorry, but it stil doesn't work.

First I thought, maybe it's because de link ends with .zip, .rar or .kml and those aren't webpages (maybe I should do something else than just "clicking"). But I've also tried the website itself (http://bocky.no.sapo.pt), even without the "http://" (so also "ftp://" would be found).
To bad, still the same message.

Have I done something wrong? (maybe I shouldn't click but "rightclick"?)
Can you tell me?