Map Scale

[Herman Lesley]

I have Garmin U S Topo. I am having some trouble determining the scale on a printed map.
 
I used to work for a land surveyor. We used maps and drew plats of surveyed property. On these plats we had a scale 1"=100', 1"=200' etc. on an engineer scale.

I print maps from U S Topo on a 8.5x11 sheet using landscape. If I print a map using Mapsource  scale 0.5 mile, how do I determine the "engineering or surveyor" scale on the printed map?  There is a line in the lower right corner of the map with 0.5 mi above it. I printed 2 maps, one showing 1 mi scale, the other 1.5 mi scale. The line on both maps measured app. 0.65" on an engineer scale. What is the actual scale on the printed map? 1"=?.

Until I can measure distance on my printed maps like on a 7.5 min Quad which is app. 1"=2000', my printed maps won't be much help in the field.

Thanks in advance

Herman

[Siskiyou]

Herman:  I do not have a good answer for you.  I agree with what you are saying but I may have a little different take on the subject because of how I use the software and my gps.  A long time ago I realized that the scale of the printed maps from US Topo was not consistent in scale.  By changing my printer preferences I could have the same map but when a ruler was placed on it the scale was different.  I just printed two maps of the same area.  I went to my printer preferences and selected landscape, borderless (received a message the image would be modified to fill the page), and selected 8.5X11 paper. 
I then printed the same area except I did not select the borderless option this time.  I got the same map but this time it had for borders with the same scale listed at the bottom.  The resulting map distance on the printed maps did not measure the same distance I obtained using the Routing Tool on the computer. 

Garmin claims the US Topo maps are comparable to U.S. Geological Survey 1:100,000-scale paper maps.
We are dealing with maps that have been scanned from USGS maps, and modified into software that can be downloaded to a gps.  I like to thing of a gps as a handheld computer that receives satellite signals.  And the handheld computer if so designed will accept certain software.  I believe the software is designed to work with the gps unit first and foremost and not provide to scale printed maps.

I use three different tools when measuring distance using US Topo.  One is the Distance/Bearing Tool in the tool bar.  The other is the Tracking Tool, and the Routing tool.  All of these will provide you with distance. 

While I use the US Topo maps on my gps and to locate geocaches as small as a 35MM film canister miles from my starting point I do not consider them close to being survey grade.  When serious hunting is taking place I have USGS Topographic Maps from the National Geographic State Series in my pocket.  I use the MapSource US Topo tools to measure distance on a map on the computer screen or when I can create a Track on the computer, or in the field creating a track and waypoints on my gps and then downloading the data to MapSource.  I then can use the software or my gps to determine the approximate distance between waypoints.  We are not dealing with surveying grade gps units or surveying grade mapping software.  In fact one of the issues in outdoor travel is that maps do not take into consideration slope distance.  Map distance is based on the earth being ironing board flat it does not take into consideration a thousand foot drop into the Grand Canyon or a trip up Pikes Peak. 

One of the best free sources of Topo maps is  www.topozone.com

Years ago a major survey monument was placed in a field in Northern California.  I do not know if the field in question changed ownership in time but with newer surveying methods it was found that surveys and maps generated using the monument were off.  The story was that the farmer moved the monument back and forth with his tractor so he could disc his field.  This resulted in major property line disputes, and the further the distance from the monument the greater the error.  So the topography did not change just the ownership.

There are some talented people who contribute who may be able to provide us with a better answer.  I am looking forward to their impute.

[xr650rRider]

Only by accident will you ever get a scale that will match an engineering scale.  The image you are printing is no more than a screen capture.  When it is sent to the printer its just a bit mapped file and the only scale it contains is relative to the screen.  The printer has an entirely different resolution than the screen.  Some graphics packages will convert the resolutions to get a pseudo-scaled image.  With Mapsource you aren't printing a vector based image where distance could be calculated.  They give you a scale that is always relative to the image you print.  If I printed the exact same area as you except that I printed an 11x17 image.  The picture of my map would be proportionally larger than yours.  The printed scale would be proportionally larger as well.  You can still use dividers and measure distances but the scale won't match an engineering scale unless by accident.  With the right software you could capture the image and then precisely measure the actual scale, then knowing the print device dpi capabilities you could scale the image to match some known scale.  You just can't do it with Mapsource out of the box.

[d_hiker]

I have figured the map scale before.  Let me printout a couple of maps tonight or tomorrow and I'll give you a step by step way to do it.  I don't remember it being too hard.  I deal with similar issues at work with information from outside sources.  I am a land surveyor and know what you are referring to.

[EsoxLucius]

That's why cartographers prefer representative fraction scales or RF.  A USGS topo Quad usually has a representative fraction scale of 1:24000 which means 1 unit of anykind (inches, cm, mm, etc.) equals 24000 of the same units on the ground.  From that, with a little math your scaling efforts are a breeze.  If you can find features on the map that correspond to a known distance, such as survey sections (one mile square), you can scale from those.

[EsoxLucius]

I have Garmin U S Topo. I am having some trouble determining the scale on a printed map.
 
I used to work for a land surveyor. We used maps and drew plats of surveyed property. On these plats we had a scale 1"=100', 1"=200' etc. on an engineer scale.

I print maps from U S Topo on a 8.5x11 sheet using landscape. If I print a map using Mapsource  scale 0.5 mile, how do I determine the "engineering or surveyor" scale on the printed map?  There is a line in the lower right corner of the map with 0.5 mi above it. I printed 2 maps, one showing 1 mi scale, the other 1.5 mi scale. The line on both maps measured app. 0.65" on an engineer scale. What is the actual scale on the printed map? 1"=?.

Until I can measure distance on my printed maps like on a 7.5 min Quad which is app. 1"=2000', my printed maps won't be much help in the field.

Thanks in advance

Herman

You set up a simple ratio.

First map is .65" = 1 mile
Second map is .65" = 1.5 miles

For the first map:

.65    1
 __=__
  1    X

.65x = 1

then divide both sides by .65

Hence, with the first map 1" will equal 1.538 miles.

Now you try it for the second map.