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Scale of the Barsoom Map

Hullo, folks,

I’ve got both the paper version of the game map of Barsoom, as well as the fabric map…

But for the life of me, I can’t figure out a measurement scale using the bits in the map at the bottom, or the divisions along the equator of the two halves of Barsoom.

Can someone give me an idea, please, of what an inch represents in Barsoom distance on the map?

Thanks, in advance. :slight_smile:


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Well, Wikipedia tells me that the circumference of Mars is 13,263 miles so if you look at the two circles it should be 13,263 miles along the equator from the left edge of the map to the right edge. And roughly half that (6,631.5 miles) from top to bottom.

I don’t have an actual printed map so I can’t measure it to get the exact “miles per inch” number for you, but it should be basic division.

Of course, distances would be a little distorted when moving from one circle to the next if not moving along the equator.

You’re right. Sofs, sofads, ads, haads, and karads are mentioned at the bottom, but I can’t find the distance measure they correspond to. We can’t use the circumference of Mars as calculated from Earth, since the distances ERB gives of Barsoom are slightly different. But we know the following from a footnote at the end of Chapter 6 of Thuvia, Maid of Mars:

  • 360 karads = 1 circumference of Mars at equator

Since Francesca Baerald’s Map contains 18 units of measure on each hemisphere of Barsoom, each of those measures must be equivalent to 10 karads

You’re right, that’s a typo. There are 18 units per hemisphere on the map for a total of 36 units. Corrected.

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Kaor JohnK,

I suppose a lot depends on the dimensions of your printed map or, more particularly, the measurement of the equator on your printed map :thinking:.

I’d measure that out and apply ERB’s calculations to a ten degree length (approximately 369 miles) and see what an inch gives you.

Later edit:
I measured the equatorial band on the fly-leaf maps inside the core-book cover. Each 20 degree section is approximately 2.9 mm; each 10 degree is approximately 1.5 mm (plus or minus a mm or two) and, thus, with some handwavium :wink: : 24/25 miles per mm–but of course that would be only across the equatorial band.

Cheers & YBMV,

Cool. Sorry if I came across as picky! Comment deleted as no longer relevant.

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Oh no worries! Glad you caught that.

The internets say the circumference of Jasoom (Earth) is about 40, 000 km at the equator - and Barsoom (Mars) is 21, 000 km at the equator, so I took a silhouette of Jasoom and placed it over the map of Barsoom.

This clears up a lot for me, as i was worried there wouldn’t be a lot of undiscovered places on Barsoom, but given the lack of ocean cover, the area playable on Barsoom is MASSIVE!!!


Hullo, folks,

Thanks to everyone who chimed in on this topic (though I do wish the folks from Modiphius would show up more often than not!), I’ve got a handle on this matter.

Thanks, all! :smile:


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Sorry, Doc-Savage, but your map is wrong. It would be correct if Barsoom had the same size as Earth. The circumference of Earth is 40,074 km at the equator, the circumference of Barsoom is 360 Karad (= 21,386.52 km) at the equator. So the diameter of Earth is 12,742 km and the diameter of Barsoom 6,807.541 km. So Earth has a diameter that is 87.175% larger than the diameter of Barsoom. If you double the diameter of a sphere, you wil quadruple its surface (because A = 4 π r²). Thus Earth’s surface is 250.344% larger than Barsoom’s.
This means that Barsoom’s surface is approx. 145,571,203.88 km². Interestingly, the surface of all of Earth’s continents together is only 3,858,796.12 km² (or 2.651%) larger.


Caranfang, I like your numbers in general as they look similar to my estimates from a few posts above, but I’m curious if you accounted for the fact that the earth’s oceans cover roughly 70% of the surface? Your calculations at the end of your post didn’t specify and I got confused by your numbers.

Thinking it through on my own, if Earth has roughly 2x the diameter it also has 2x the radius, so 4x the surface area using the same area equation you quoted. But because of the oceans, Earth has only 0.3*4x or 1.2x the land area. (1.2x would be 120%.) That’s really different from your number, but I can’t see why we should be so far apart.

I’m also impressed by the fact that you were able to type a “pi” symbol. I’m not sure I can do that, unless you did a copy-paste from Word. :slight_smile:

Standard HTML entities can be used such as π to generate π.
§ gives §
& gives &
± gives ±
µ gives µ

𝒪𝓃ℯ 𝒸𝒶𝓃 ℯ𝓋ℯ𝓃 𝒹ℴ 𝓈𝒸𝓇𝒾𝓅𝓉 𝓌𝒾𝓉𝒽 𝒾𝓉! 𝔄𝔫𝔡 𝔞𝔩𝔰𝔬 𝔣𝔯𝔞𝔨𝔱𝔲𝔯 𝔞𝔰 𝔴𝔢𝔩𝔩.

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I’ve made these calculations because Doc-Savage simply copied a map of Earth on a Map of Barsoom ignoring the fact that Earth is much larger that Barsoom. I’ve used the circumference of 360 karad given on the Barsoom map and not the one of the real Mars and used it to calculate the diameter and the surface of Barsoom. Then I compared these values with those of our Earth. I did not use rough estimates but real values. Thus Earth’s radius is not two times Barsoom’s radius but only around 1.87 times. That means that that you have to multiply Earth’s land area with ~3.5 (and not 4) to get the value you seek: 3.5 x 29.3% = 102.55%.

BTW I’ve used 149.430.000 km² (=29.3%) for Earth’s land area. Other sources give slightly different values.

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Ah, it’s the “circumference of 360 karad given on the Barsoom map and not the one of the real Mars” part that slipped past me. I think that explains why our calculations differ. :smiley:

As Caranfang wisely pointed out, I didn’t think through my projections properly when making the above map. Here is what it should look like. Correct me if I’m again wrong. Despite Jasoom being twice the size of Barsoom, the lack of water cover opens up far more areas to play. Barsoom-Jasoom

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