Discussion: Tool for measuring distance on topo map...?

I've seen teams using a tool with a small wheel that they roll along their intended route to measure distance on a topo map. What are those called? Any specific make/model recommendations?

Thanks.

I believe it is called an Opisometer.
https://en.wikipedia.org/wiki/Opisometer

This is the best one that I have ever used...

Scalex Map Wheel

Is it really a necessary expense? Any Nav would be a decent to good judge of distance anyway. How common is this bit of kit in AR teams?

I would say very common when you get the maps ahead of time.

Especially if you get maps only 1 hour before the start.

Cheers. The Scalex Map wheel you linked to there is like €100 to deliver to the Emerald Isle. Any other "nearly as good" but cheaper recommendations?

Also do you use any kind of formula to work out your predicted pace with the climbing in that measurement considered?

A piece of string worked well for me.

Lay it along the route and set against the map scale.

Mike closer to home http://scalex.com/uk/index.php?main_page=product_i...

formula to work out predicted pace with climbing = experience.

and a healthy dose of Mark Lattanzi's rules for navigating (at night)
1) Traveling at night is much slower than in the daytime.
2) Know exactly where you are when dusk comes.
3) Traveling at night is much slower than you think.
4) You need to be more careful about taking and following bearings.
5) Traveling at night is much slower than walking in molasses.
6) Use bigger point features and linear features as much as possible.
7) Traveling at night is much slower than hiking with snails.
8) When in doubt, you probably haven’t gone far enough.
9) Traveling at night is much slower than hopping with a stick in your leg.

http://www.navigationtips.com/wordpress/?p=391

At Wilderness Traverse 2015, the sneaky ;) race directors / course designers did a viscously good job of positioning the checkpoints such that the estimated time for the various route options was always almost identical (e.g. longer biking route on pavement but faster average speed versus the shorter gravel/dirt trail option). Thus, being able to measure the distances on the map accurately was key. We re-measured multiple times because the comparisons were so close. Having the wheel made this easier and quicker; priceless when you are pressed for time after getting the maps just before the race.

Hey, we gave you the maps 12 hours before the race! Lots of time to measure distances *and* enjoy your beauty sleep. ;)

Here is another place to buy map measurers in the U.K. When I can't find what I want at O-Store.ca, this is the 2nd place I look. The shipping times and costs to Canada have been quite reasonable.
http://www.compasspoint-online.co.uk/cgi-bin/sh000...

You know that I sleep 9 hours a night! And I was tasked with being Phatty's bike prep slave...

With ScaleX you need small person hands to use those little buttons and a second person from the 1990s to read the grayscale digital screen.

While it may be a little hairy I just pull out my left nut. It's a topographic map, why would you use a tool originally invented to measure flat elevation distances say of a stretch of water. ScaleX my ass, scale this.....on a 1:24,000 scale map my nut can prefectly gauge the steepness of the terrain represented on the map plus as an added bonus it factors such things as the fauna, predicts the weather, tells me what time it is. Now you know why I do not wear a watch and have been on the DL since a terrible paper cut in 2014. ScaleX may come with a velvet padded case, but let me just say my left nut rests easy when it's not rolling.

Joking aside ScaleX is great.

Wow a real life paper cut survivor. Credit to you man for pulling through that.