measuring land area on maps

[maps]

I am curious to know if there is a way to measure land area of a map.

(see attachment for example, in which I would like to know the land areas of the yellow part of the map...)

There must be a faster way than counting pixels!

[Myrddin]

- New layer;

- draw a line across the scale (to whatever distance is up to you);

- move and rotate (use the right mouse button and drag for free-rotation) the line over the desired land mass and measure away.

Be sure to remember how long your line was, which is told live as you draw it in the bottom-left of the screen. Bear in mind, though, it may only be a rough estimate; the accuracy depends on you.

It will entail some counting, but not as much as counting each pixel individually.

Does this quicken your tedious task?

[Rick Brewster]

Actually here's what I would do. I would take advantage of the built-in centimeters/DPI system.

First, draw a red line while holding the shift key from the "0" to the "100" in the scale at the bottom of the image. Note how long the line is, in pixels (this is printed in the status bar in real time). We'll call this number X.

Divide X by 100.0. We'll call this number Y.

Go to Image -> Canvas Size, and type Y in for "Resolution:" and also change it to "pixels / cm" instead of "pixels / inch." Then click OK.

Make sure that in the top row of the toolbar, it lists "Units:" as Centimeters, and not Pixels.

At this point you can now do several things:

1) Draw lines between 2 different points to measure distance "as the bird flies." The length will be listed in centimeters, so just mentally replace the word centimeters with kilometers.

2) Use the magic want to click on various areas of the map and obtain an estimate of area.

For example, I found X to be about 150.0 (thus, Y = 1.5). Using the magic wand, I clicked on the most top-left blue forest area. It was counted to be 2,291 pixels square which was auto-converted to 1,018.22 centimeters square, which for us means 1,018.22 kilometers square.

[maps]

this is great, thanks very much for your help Rick!

Related to the same project:

Another map I have has very unclear color patterns, so I would like to recolor it. The attachment shows in the legend which parts of the map are important. The yellow part can be selected fairly easily with the magic wand, but especially the grayish/purple area is much more difficult. I have tried to work with the histogram and adjustment functions, but have not been successful.

Can you provide some tips as to

a. how to most precisely select the gray area?

a. how to recolor the gray area to a solid color?

[Ego Eram Reputo]

this is great, thanks very much for your help Rick!

Related to the same project:

Another map I have has very unclear color patterns, so I would like to recolor it.

You should probably ask this question again in a new thread as it doesn't relate to the original title.

Before you do, have you tried search? http://www.getpaint.net/search.html

[Ash]

Dup layer, on new layer add More Saturation.

Select the colors easily. go back to the layer of the original map.

[Logmeister]

I am curious to know if there is a way to measure land area of a map.

Hey, I know you've already gotten advice on this, but I think this method will be MUCH faster.

Let me know if my method is incorrect. Hope this helps a lot!

(And I realize my typo in step two )

[Rick Brewster]

Logmeister, that's basically exactly what I said to do above. Except I included steps to calibrate the DPI system so that it tells land mass in kilometers (well, centimeters).