Red Sea map

[Nescio]

The Red Sea random map is quite nice (thank you, @elexis).

Spoiler

Minor issues:

• Suez canal didn't exist
• Qatar is a peninsula, not an island
• There is no large bodies of water on the Eritrean-Ethiopian border

However, in Antiquity the name “Red Sea” was applied to all waters surrounding the Arabian peninsula (i.e. Gulf of Suez, Gulf of Aqaba, Red Sea, Bab-el-Mandeb, Gulf of Aden, Arabian Sea, Gulf of Oman, Strait of Hormuz, Persian Gulf), which allowed people to sail from Egypt to Mesopotamia and Iraq. Therefore it would be nice if the heightmap could be extended to the east:

Unfortunately, the narrowness of the straits prevents 0 A.D. ships from passing.)

[Nescio]

Also, the Aegean Sea random map doesn't look like the Aegean at all:

[elexis]

8 minutes ago, Nescio said:

The Red Sea random map is quite nice (thank you,

Credit goes to _kali.

13 minutes ago, Nescio said:

it would be nice if the heightmap could be extended to the east

It's easily possible to move the heightmap:

 * wget https://eoimages.gsfc.nasa.gov/images/imagerecords/73000/73934/gebco_08_rev_elev_C1_grey_geo.tif
 * lat=22; lon=41; width=30;
 * gdal_translate -projwin $((lon-width/2)) $((lat+width/2)) $((lon+width/2)) $((lat-width/2)) gebco_08_rev_elev_C1_grey_geo.tif red_sea.tif
 * convert red_sea.tif -resize 512 -contrast-stretch 0 red_sea.png

Problem is that it heavily influences balancing, all players are supposed to have roughly equal chances to victory at gamestart, but often the game has already decided after pressing the Start button.

16 minutes ago, Nescio said:

• Qatar is a peninsula, not an island 
• There is no large bodies of water on the Eritrean-Ethiopian border 

Pyrogenesis only has support for one level water plane, but in the desert some areas are dry despite being below water level (for the same reason, the Nile on Lower Nubia has few water).

18 minutes ago, Nescio said:

Suez canal didn't exist 

(Same with the Nile dams on Lower Nubia)

One can add some code to modify the terrain artificially afterwards. (Fixing it in atlas means the fixes are lost if one recenters the map)

[Nescio]

42 minutes ago, elexis said:

It's easily possible to move the heightmap:

 * wget https://eoimages.gsfc.nasa.gov/images/imagerecords/73000/73934/gebco_08_rev_elev_C1_grey_geo.tif
 * lat=22; lon=41; width=30;
 * gdal_translate -projwin $((lon-width/2)) $((lat+width/2)) $((lon+width/2)) $((lat-width/2)) gebco_08_rev_elev_C1_grey_geo.tif red_sea.tif
 * convert red_sea.tif -resize 512 -contrast-stretch 0 red_sea.png

Thanks! I've never made heightmaps before.

I don't quite understand the coordinates, though. 41, 22 is in Macedonia.

Edited May 12, 2019 by Nescio

[Guest]

lat 22, lon 41 should be somewhere in west Saudi Arabia. Maybe you swapped lat and lon?

https://www.openstreetmap.org/#map=6/21.033/42.122

Edited May 12, 2019 by Guest
added link

[elexis]

That code is posted in the mapscript.

According to https://tools.wmflabs.org/geohack/geohack.php?pagename=Red_Sea&params=22_N_38_E_region:EG_type:adm1st_scale:100000000 which is linked from https://en.wikipedia.org/wiki/Red_Sea I didn't confuse latitude / longitude.

Chosing a different heightmap is an iterative process, one has to gradually change decimal places until one get's the optimum.

[Guest]

4 minutes ago, elexis said:

According to https://tools.wmflabs.org/geohack/geohack.php?pagename=Red_Sea&params=22_N_38_E_region:EG_type:adm1st_scale:100000000 which is linked from https://en.wikipedia.org/wiki/Red_Sea I didn't confuse latitude / longitude. 

The heightmap is correct. But as said above, lat 41, lon 22 could be Macedonia.

[Nescio]

26 minutes ago, (-_-) said:

lat 22, lon 41 should be somewhere in west Saudi Arabia. Maybe you swapped lat and lon?

Oops, you're right: 22, 41 is in Arabia, 41, 22 in Macedonia. And I've also found the source image area: https://visibleearth.nasa.gov/grid.php

Now, suppose I would want to make a heightmap along the 0° meridian (e.g. France), how to combine two images?

Edited May 12, 2019 by Nescio
lat, lon

[Nescio]

Anyway, moving the centre slightly to 24, 46 produced the map I wanted:

gdal_translate -projwin 30 40 62 8 gebco_08_rev_elev_C1_grey_geo.tif red_sea.tif
convert red_sea.tif -resize 512 contrast-stretch 0 red_sea.png

Edited May 12, 2019 by Nescio
lat, lon

[wowgetoffyourcellphone]

9 minutes ago, Nescio said:

Ptolemies on the left, Nabataeans in the middle (), Persians on the right. Noice. 

[Guest]

(I always find these maps odd due to the scale.)

12 minutes ago, Nescio said:

Now, suppose I would want to make a heightmap along the 0° meridian (e.g. France), how to combine two images?

Lon 0 Should be included in the C1 image. But if you want a nicer heightmap, you would need to include B1 too probably.

After the same old commands for both images done seperately you can combine the two using `convert +append 1.png 2.png out.png` + for horizontal side-by-side. - for vertical.

[elexis]

1 minute ago, (-_-) said:

I always find these maps odd due to the scale.

On the one hand one can change the mapscale, on the other hand maps that don't use heightmaps also use custom scales, on the foot there are some heightmap maps that use more proportionate scales (ratumacos).

21 minutes ago, Nescio said:

how to combine two images?

Mediterranean:

Quote

 * wget https://eoimages.gsfc.nasa.gov/images/imagerecords/73000/73934/gebco_08_rev_elev_{A,B,C,D}{1..2}_grey_geo.tif
 * gdal_merge.py -o world.tif gebco_08_rev_elev_{A,B,C,D}{1..2}_grey_geo.tif
 * lat=46; lon=14; width=58;
 * gdal_translate -projwin $((lon-width/2)) $((lat+width/2)) $((lon+width/2)) $((lat-width/2)) world.tif mediterranean.tif
 * convert mediterranean.tif -resize 512 -contrast-stretch 0 mediterranean.png

There are more examples, Hellas picks a random subset that meets some requirements (between 20% and 30% water), or Jebel Barkal which loads an Atlas map (you can load the image in atlas and save as a PMP file and load that in the random map, but that means one can't recenter it afterwards), Lower Nubia combines a heightmap and a composites to get a more precise shape of the nile, Elephantine uses OpenStreetMap data (since the blue marble data is very blurry when zooming in to that level). The comments are all in the headers of the JS files.

[Guest]

21 minutes ago, elexis said:

but that means one can't recenter it afterwards

Why not? You can shift and rotate the Atlas heightmap anyway you want. f(x, y) => (x + transformation, y + transformation)

[elexis]

Translating the map means terrain is lost and has to be filled with something else. Since it uses a heightmap, the blank region was intended to be filled by the heightmap data.

[Guest]

Ah, I was speaking from purely a JB PoV.

[Nescio]

50 minutes ago, elexis said:

Quote

 * wget https://eoimages.gsfc.nasa.gov/images/imagerecords/73000/73934/gebco_08_rev_elev_{A,B,C,D}{1..2}_grey_geo.tif
 * gdal_merge.py -o world.tif gebco_08_rev_elev_{A,B,C,D}{1..2}_grey_geo.tif
 * lat=46; lon=14; width=58;
 * gdal_translate -projwin $((lon-width/2)) $((lat+width/2)) $((lon+width/2)) $((lat-width/2)) world.tif mediterranean.tif
 * convert mediterranean.tif -resize 512 -contrast-stretch 0 mediterranean.png

Thanks again! Interestingly, the eight tiles are together 116 MB in size, merging them creates a file of 933 MB.

58 minutes ago, (-_-) said:

(I always find these maps odd due to the scale.)

True, but it can also be used for smaller areas, of course, e.g. Sicily [12 40 16 36]:

Spoiler

Or the Strait of Messina [15.4 38.4 15.8 38.0]:

Spoiler

Edited May 12, 2019 by Nescio
Zancle

[elexis]

(Maps with two opposing sides have the same area and same maximum traderoute length ideally. Differences become very pronounced with normal and smaller mapsizes. The number of mines, trees and hunt is proportional to the area.)

[Nescio]

Don't worry, I have no ambition to start creating any new maps. All I wanted to know is how to tweak the area covered by the Red Sea map.

[elexis]

22 hours ago, Nescio said:

tweak the area covered by the Red Sea map

Updating the coordinates in the command in the JS file allows you or anyone you might distribute it to to perform a consecutive update to the heightmap.

[Guest]

Visible Earth heightmap is not that large. And 0AD would need only C1. I wonder if a single copy can be kept and a library built around it would be a good idea.