Program to calculate size of map and point to point distance.

[Elros]

Hello, i have a little problem, sorry for my english is not my first lenguage, im italian.
Anyone know one program can calculate travel time, or distance point to point of my map?

I have made my own map hand drawn and updated with Photoshop.
Now i want determinate the size of my map basing on 1 day of travel is 15-20 Kilometers, approximately 10-12 miles.

Is that possible with one cartography program?

Edit:
I am also open to external programs besides photoshop

[Azélor]

Measuring area is somewhat easy.

1-The first requirement is knowing what map projection you are using.
I am going to assume you are using an equirectagular map projection. There are no default map projection but this is a very common one to use unless you have something specific in mind.

2- You need to change the projection of an image using a software like G.Projector : https://www.giss.nasa.gov/tools/gprojector/
G.projector now accepts plenty of different projections as input not just equirectangular.
Pick an equal area map projection such as Mollweide https://en.wikipedia.org/wiki/Map_projection#Equal-area
It will allow you to measure areas.
ALWAYS KEEP THE ORIGINAL, WORK ON A COPY

3- open the image in photoshop.
On a new layer, paint the area you want to measure in a different colour. Use the pen, not the pencil as you need sharp (pixelated) borders if you want to be accurate.
Using the magic wand and the histogram (windows/histogram) find the total surface (in pixel) of the map (water and earth). Write it down somewhere.
Find the size of the area you are interested in.

Divide the area by the size of the world, this gives you a percentage.
Multiply this percentage by the size of the world in square kilometre, ( or square miles in you live in US or Myanmar) to get the actual size of the area.
For reference, Earth is 510 000 000 km2. So 10% would be 51 000 000 km2.

You don't really need to know the scale of your map, just the % of the world covered and the size of the world.

---

The find a distance between two points: I think it can be done by using trigonometry where ''a'' is the difference in latitudes, ''b'' is the difference in longitudes and ''c'' is the distance that you are trying to find.
The ''b'' will change depending on the latitude as the distances get shorter the closer you get to the poles.

[Elros]

Measuring area is somewhat easy.

1-The first requirement is knowing what map projection you are using.
I am going to assume you are using an equirectagular map projection. There are no default map projection but this is a very common one to use unless you have something specific in mind.

2- You need to change the projection of an image using a software like G.Projector : https://www.giss.nasa.gov/tools/gprojector/
G.projector now accepts plenty of different projections as input not just equirectangular.
Pick an equal area map projection such as Mollweide https://en.wikipedia.org/wiki/Map_projection#Equal-area
It will allow you to measure areas.
ALWAYS KEEP THE ORIGINAL, WORK ON A COPY

3- open the image in photoshop.
On a new layer, paint the area you want to measure in a different colour. Use the pen, not the pencil as you need sharp (pixelated) borders if you want to be accurate.
Using the magic wand and the histogram (windows/histogram) find the total surface (in pixel) of the map (water and earth). Write it down somewhere.
Find the size of the area you are interested in.

Divide the area by the size of the world, this gives you a percentage.
Multiply this percentage by the size of the world in square kilometre, ( or square miles in you live in US or Myanmar) to get the actual size of the area.
For reference, Earth is 510 000 000 km2. So 10% would be 51 000 000 km2.

You don't really need to know the scale of your map, just the % of the world covered and the size of the world.

---

The find a distance between two points: I think it can be done by using trigonometry where ''a'' is the difference in latitudes, ''b'' is the difference in longitudes and ''c'' is the distance that you are trying to find.
The ''b'' will change depending on the latitude as the distances get shorter the closer you get to the poles.

Hi, thanks for replying, I'm using this map here.




I don't know what projection it is, I don't understand much about these things.
Isn't there an easier method?

[Azélor]

I don't think there is a faster method. Photoshop was not designed for cartographers but for artists in general, therefore it lack some tools and we have to use others software.
While this method looks complicated, it gets really easy once you do it a couple of times.

[Falconius]

You should note that Azelor is talking about a whole world map. So if you were to go with that method to get the area of the island, you'd have to put the island by itself in a world map.

[Azélor]

You should note that Azelor is talking about a whole world map. So if you were to go with that method to get the area of the island, you'd have to put the island by itself in a world map.

Oh, you are right. It's going to be a little bit more complex.
You don't need to have the whole world, you can do it using only a portion of it.
G.projector will ask to enter the edges of the map (longitudes and latitudes).
If you can figure out the coordinates, you can do it with only a section of the map.
But you will also have to find the percentage of the world covered by that specific section.

[waldronate]

Your island is less than about 400 miles across: the errors inherent in the map image will overwhelm any likely measurement errors relating to projection. In short, because the island is smallish, you can mostly ignore the projection. If the world itself is flat, then projection is an irrelevant concept.

Now that your map is declared as something that can be measured with a ruler, you need a tool that will measure those distances. There are many tools out there that will do that (try searching for "measure distance on an image web page" in your favorite search engine. Then define that one pixel in your image is X real-world units as shown by your scale bar.

A less complex technique use a physical ruler to measure the scale bar and your desired path directly onscreen, then do the math to convert scale units to real-world units. This also works if you print out the map. The scale bar is the critical part here.

[Redrobes]

Also if you want to measure area then get your map into a black and white image where the island is all black and the background is all white - using contrast or just painting it in. Then you can use the histogram view on most paint packages to count up the percent of the image which is white and black. From that you can usually calculate the area of a complex shaped island real quick.

So if you have a 1000x1000 image and you have a scale bar showing that 100 pixels across is 10 miles then each pixel is 10 / 100 miles or 0.1 miles each pixel. So if your histogram reads off that your island in black is 27.3% of the total white background image, then you have 27.3% of 1000 x 1000 x 0.1 x 0.1 square miles. Which is 0.273 x 100 x 100 which is 2730 square miles.

[Elros]

I don't think there is a faster method. Photoshop was not designed for cartographers but for artists in general, therefore it lack some tools and we have to use others software.

Are there other softwere that can help me?

While this method looks complicated, it gets really easy once you do it a couple of times.

I think trying nothing costs to me. Thanks for the advice

[Elros]

Oh, you are right. It's going to be a little bit more complex.
You don't need to have the whole world, you can do it using only a portion of it.
G.projector will ask to enter the edges of the map (longitudes and latitudes).
If you can figure out the coordinates, you can do it with only a section of the map.
But you will also have to find the percentage of the world covered by that specific section.

It seems complex