Determining Steepness of Grade

Quoted message said:

I find myself wondering, though, how various posters obtain the elevation change data.

I use a Garmin GPS and take the elevation reading from it. Although a GPS elevation reading itself
isn't exact, they're plenty good enough to note the elevation at the top of a hill and subtract the
elevation at the bottom and that value is the hill's elevation change. I've found that if I do this
on different days, my GPS elevation reading at the top and bottom of a hill may vary a bit--but
when you subtract the difference between them (the elevation change), it is pretty much
consistently the same.

In other words, if you take a GPS elevation reading for the top of a hill, also take the elevation
reading for the bottom of the hill right away. Don't take the second reading on a different day.

Brian Tailwind/V-Rex

George,

Though not as accurate as GPS, Adventure Cycling (and perhaps your LBS) carries an inclinometer.

Check it out at:

https://www.adventurecycling.org/cgi-shl/webc.exe/advsales/st_prod.html?p_prodid=554&p_catid=32&sid=4o3xA2j4

Ben

Quoted message said:

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>Burley Canto>>>>

George,

Quoted message said:

I find myself wondering, though, how various posters obtain the elevation change data.

No electronics, but it works.

adventurecycling.orgst prod.htmlOpen ↗
d=4o3xBFhn

You'll need to paste this long address into you browser.

Warren

I use "Topo-USA" Delorme's map program, it calculates %grade for me. It will also tell me the
elevations at any point in a route, so I could calculate it myself.

--
Gene O _ \ _/\,%) (*)--(*)

[email hidden] home.att.net~gene8Open ↗

"Vol" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

In various threads here, posters refer to steepness of a grade in terms of percentage.

The math is simple: elevation change divided by distance traveled times 100 yields percentage
of grade.

I find myself wondering, though, how various posters obtain the elevation change data.

If anyone feels like providing some education, I'm ready to learn. It would be mildly interesting
to know if that knee-burner is a big nasty seven or more like a four.

George

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

I use "Topo-USA" Delorme's map program, it calculates %grade for me. It will also tell me the
elevations at any point in a route, so I could calculate it myself.

TopoUSA only reports what it can measure from the data (topo contours and road position). Usually
both are very wrong. Road cuts and fills (used to level out the road)usually do not warrant a shift
in contour lines and are invisible to TopoUSA.

Most GPS have a vertical accuracy of +/- 10-20m So using the relative difference on elevation as
some have mentioned may or may not always work either.

At best you will only get an approximation.

Quoted message said:

--

Cletus D. Lee Bacchetta Giro Lightning Voyager clee.orgclee.orgOpen ↗
- Bellaire, TX USA -

"Cletus Lee" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

Most GPS have a vertical accuracy of +/- 10-20m So using the relative

difference on elevation

Quoted message said:

as some have mentioned may or may not always work either.

At best you will only get an approximation.

In open country, where the signal from a couple of low-elevation satellites is strong, the GPS
altitude measurements can get to be quite good on my Garmin. They compare well with posted
elevations at divides for example, and some differential measurements I've taken under the same
conditions correspond well with the gross topo differentials.

As a general rule, though, GPS altitudes and earth's surface can't be trusted.

Fred Klingener

"Fred Klingener" <[email hidden]> wrote in message
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Quoted message said:

"Cletus Lee" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

In article <[email hidden]>, [email hidden]
says...

Quoted message said:

Most GPS have a vertical accuracy of +/- 10-20m So using the relative

difference on elevation

Quoted message said:

as some have mentioned may or may not always work either.

At best you will only get an approximation.

In open country, where the signal from a couple of low-elevation satellites is strong, the GPS
altitude measurements can get to be quite good on my Garmin. They compare well with posted
elevations at divides for example, and some differential measurements I've taken under the same
conditions correspond well with the gross topo differentials.

As a general rule, though, GPS altitudes and earth's surface can't be trusted.

Fred Klingener

In my experience, the differential measurement is consistently quite good. More so than the absolute
elevation. In other words, noting the elevation change between point A and point B will almost
always give the same result on on any given day even though the absolute elevation reading at point
A and point B may be different by 30 feet or more on different days.

For example, if today's elevation reading is 30 feet higher at the top of a hill than yesterday's
reading, it will also (most likely) be about 30 feet higher on the bottom of the hill too. So
when you subtract the difference to calculate the height of the hill--the result will be very
near the same.

Brian

The precision of GPS units will be somewhat dependent on the type of units used. I have purchased
several of the Garmin hand held units for our Survey group. I have tested them against points of
known elevation. During a five minute episode I have seen them vary as much as 20 to 30 ft on both
sides of the published elevation.

I also have GPS units which are capable of accuracy in the centimeter range (dependent upon the
network we use.)

A 30' error in a mile will be about 0.5% which is probably no big deal. A 30" error in 500' is
a 6% error.

As long as you use caution and common sense I would think that the GPS derived elevations would
yield acceptable results.

William L. Higley, Sr., P.L.S. Vision R-50

"bandjhughes" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

"Fred Klingener" <[email hidden]> wrote in message

news:<[email hidden]>...

Quoted message said:

Quoted message said:

"Cletus Lee" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

Most GPS have a vertical accuracy of +/- 10-20m So using the relative

difference on elevation

Quoted message said:

as some have mentioned may or may not always work either.

At best you will only get an approximation.

In open country, where the signal from a couple of low-elevation

satellites

Quoted message said:

Quoted message said:

is strong, the GPS altitude measurements can get to be quite good on my Garmin. They compare
well with posted elevations at divides for

example,

Quoted message said:

Quoted message said:

and some differential measurements I've taken under the same conditions correspond well with the
gross topo differentials.

As a general rule, though, GPS altitudes and earth's surface can't be trusted.

Fred Klingener

In my experience, the differential measurement is consistently quite good. More so than the
absolute elevation. In other words, noting the elevation change between point A and point B will
almost always give the same result on on any given day even though the absolute elevation reading
at point A and point B may be different by 30 feet or more on different days.

For example, if today's elevation reading is 30 feet higher at the top of a hill than yesterday's
reading, it will also (most likely) be about 30 feet higher on the bottom of the hill too. So
when you subtract the difference to calculate the height of the hill--the result will be very
near the same.

Brian

I don't know what you're talking about. Topo-USA works in 1' increments and has nothing to do with
contour lines when calculating elevation. When calculating the grade of a hill, you can measure the
elevation at the bottom and the elevation at the top, all within 1 foot, then measure the distance
to calculate %grade. I've found Topo to be very accurate especially compared to GPS and cycle
altimeters. When Topo gives an altitude of a point it compares exactly to all references I can find,
which is far more than I can say for any consumer GPS I've seen. The references to which I refer are
official altitude markers at passes also, since I'm a pilot, I have charts for airport elevations
and Topo agrees exactly with those. I've seen GPS units vary by 50 feet in a few minutes without
moving an inch. That goes for both Magellan and Garmin. What evidence do you have for the inaccuracy
of Topo? I will agree that road position for very short and curvy sections are not especially
accurate in Topo, but for the length of the hill from bottom to top the total elevation gained, and
that's what is important in this calculation, it is extremely accurate.

Gene

"Cletus Lee" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

I use "Topo-USA" Delorme's map program, it calculates %grade for me. It will also tell me the
elevations at any point in a route, so I could calculate it myself.

TopoUSA only reports what it can measure from the data (topo contours and

road position).

Quoted message said:

Usually both are very wrong. Road cuts and fills (used to level out the

road)usually do not

Quoted message said:

warrant a shift in contour lines and are invisible to TopoUSA.

Most GPS have a vertical accuracy of +/- 10-20m So using the relative

difference on elevation

Quoted message said:

as some have mentioned may or may not always work either.

At best you will only get an approximation.

Quoted message said:

--

Cletus D. Lee Bacchetta Giro Lightning Voyager clee.orgclee.orgOpen ↗
- Bellaire, TX USA -

How about the roads near N37° 23.235' W80° 23.584' and N37° 21.247' W80° 32.022' First, the roads
are not where the map says they are and this may be its biggest problem. Second, none of the cuts
and fills are expressed in the topography or the underlying data points. I believe the contour lines
are derived by TopoUSA from selected input points (which are not necessarily closely spaced or even
in a uniform grid.)

Since you are a pilot, I think you should get out of the clouds and get your feet on the ground.
Remember that those airport elevations that TopoUSA agrees with are flat places and near known
input points.

I have written computer contouring mapping programs and have spent the last 40 years intimately
acquainted with geological and topographical maps. I think the most accurate (in the US) topo maps
are those published by the USGS. They are only accurate at the surveyed Bench Marks. Even these are
sometimes in error. And especially those in remote mountainous areas where these grades are being
determined. Everything on a USGS topo map between Bench Marks are guesses. The guesses may be based
upon stereo photographic information and made by a computer, but they are still guesses. The closer
a point is to a BM, the more accurate it tends to be. I believe TopoUSA uses a similar photographic
method to suppliment known points.

As for GPS. I registered my GPS two days earlier at a USGS BM about 40 miles from the point where
this picture was taken. clee.orgimage029.htmOpen ↗
clee.orgimage030.htmOpen ↗

The Blueridge Parkway sign called the elevation of the overlook 2400' the GPS registered 2370' the
Topo map in the GPS memory (Not TopoUSA) said that I was on the 2100' contour. The location of the
GPS in relation to the road on the map said that I was about 50' NW of the BRP. IIRC, the data
point from the GPS when plotted on TopoUSA was about as inaccurate as the topo data in the GPS. I
will try to find the track for that trip and give you the coordinates for that point so you can
compare for yourself.

BTW, TopoUSA (v4.0) is a fine product as long as you consider it's limitations. Here are some
impressive jpegs of the kind of things that TopoUSA can do well.

clee.orgdefault.cfmOpen ↗ Click on each one to enlarge.

You also may be interested in this review of TopoUSA 4.0 by Alex Wetmore:
phred.orgtopo4.htmlOpen ↗

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

I don't know what you're talking about. Topo-USA works in 1' increments and has nothing to do with
contour lines when calculating elevation. When calculating the grade of a hill, you can measure
the elevation at the bottom and the elevation at the top, all within 1 foot, then measure the
distance to calculate %grade. I've found Topo to be very accurate especially compared to GPS and
cycle altimeters. When Topo gives an altitude of a point it compares exactly to all references I
can find, which is far more than I can say for any consumer GPS I've seen. The references to which
I refer are official altitude markers at passes also, since I'm a pilot, I have charts for airport
elevations and Topo agrees exactly with those. I've seen GPS units vary by 50 feet in a few
minutes without moving an inch. That goes for both Magellan and Garmin. What evidence do you have
for the inaccuracy of Topo? I will agree that road position for very short and curvy sections are
not especially accurate in Topo, but for the length of the hill from bottom to top the total
elevation gained, and that's what is important in this calculation, it is extremely accurate.

Gene

"Cletus Lee" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

In article <[email hidden]>, [email hidden]
says...

Quoted message said:

I use "Topo-USA" Delorme's map program, it calculates %grade for me. It will also tell me the
elevations at any point in a route, so I could calculate it myself.

TopoUSA only reports what it can measure from the data (topo contours and

road position).

Quoted message said:

Usually both are very wrong. Road cuts and fills (used to level out the

road)usually do not

Quoted message said:

warrant a shift in contour lines and are invisible to TopoUSA.

Most GPS have a vertical accuracy of +/- 10-20m So using the relative

difference on elevation

Quoted message said:

as some have mentioned may or may not always work either.

At best you will only get an approximation.

Quoted message said:

--

Cletus D. Lee Bacchetta Giro Lightning Voyager clee.orgclee.orgOpen ↗
- Bellaire, TX USA -

--

Cletus D. Lee Bacchetta Giro Lightning Voyager clee.orgclee.orgOpen ↗
- Bellaire, TX USA -

is there a difference between steepness of grade and elevation gain? i could see topo being accurate
for elevation gain calculations . however i dont belive the roads that are drawn on the map are
accurate enough for measuring the grade. inaccurate placement of road details woulr alter the grade.
i find the garmin legend GPS accurate for elevation if the sateelitte reception is over 5sat . i
find it than matches or could be more accurate than topo maps. however if the reception is poor or
minimAL 3 SAT the elevation could be off a while lot, much more than 500feet even though the margin
of error on th gps is showing 150 foot circle. i find that the margin of error circle is more
accurate with horizontal(land). when the gps margin of error circle is under 20 feet i find the
elevation extremely accurate. i use it to resset my sunnoto altimater

Quoted message said:

Topo-USA works in 1' increments and has nothing to do with contour lines when calculating
elevation.

But it does use its own internal digital elevation model. Which is prolly derived from the USGS. And
doesn't have 1' resolution. They seem to have a good method of interpolating elevations between
known values though.

I sometimes use TOPO-USA here at work if I have no other data available for an area. I have checked
it against my known High Precision Geodetic Network (HPGN) points, and it does seem very good.

George Bearden Geographic Information System (GIS and Automated Mapping) Group Leader City of Fresno

Most climbs or hills are curves in reality and "grade" is accurate only at the point at which the %
grade is measured. Accurate grades can not be calculated from taking the difference between the
beginning elevation and the final elevation unless one is measuring a constant grade portion of a
climb. Using elevations from the bottom and top of a mountain or hill will not give you % grade,
only change in elevation.

"mike" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

is there a difference between steepness of grade and elevation gain? i could see topo being
accurate for elevation gain calculations . however i dont belive the roads that are drawn on the
map are accurate enough for measuring the grade. inaccurate placement of road details woulr alter
the grade.

"Dennis Tresenriter" <[email hidden]> wrote in message
news:BO6Ia.23544$vq.3980@sccrnsc04...

Quoted message said:

Most climbs or hills are curves in reality and "grade" is accurate only at the point at which the
% grade is measured. Accurate grades can not be calculated from taking the difference between the
beginning elevation and the final elevation unless one is measuring a constant grade portion of a
climb. Using elevations

from

Quoted message said:

the bottom and top of a mountain or hill will not give you % grade, only

change

Quoted message said:

in elevation.

Most people want to know the average grade for the hill which can be found by noting the change in
elevation divided by the horizontal distance traveled (using the same units) x 100. Not to many
people are interested in the grade at every discrete point. Your argument would mean that even a
flat and level dry lake bed like the Salt Flats would probably have an extreme grade at some point
if you happen to ride over a rock.

Vol said:

In various threads here, posters refer to steepness of a grade in terms of percentage.

The math is simple: elevation change divided by distance traveled times 100 yields percentage
of grade.

Strictly speaking, percent grade is elevation change divided by the horizontal distance traveled
multiplied by 100. However, for most real world roadway grades, the distance traveled along the
roadway is sufficiently close enough to the horizontal component of this distance for the error
to be small.

Tom Sherman - Various HPV's Quad Cities USA (Illinois side)

brian hughes said:

Most people want to know the average grade for the hill

I want to know the maximum grade which is sustained for any distance of more than ten yards or so.

Guy
===
** WARNING ** This posting may contain traces of irony. chapmancentral.comchapmancentral.comOpen ↗ Advance
notice: ADSL service in process of transfer to a new ISP. Obviously there will be a week of downtime
between the engineer removing the BT service and the same engineer connecting the same equipment on
the same line in the same exchange and billing it to the new ISP.

"Just zis Guy, you know?" skrev...

Quoted message said:

Quoted message said:

Most people want to know the average grade for the hill

I want to know the maximum grade which is sustained for any distance of more than ten yards or so.

I usually just want someone to tell me its gonna end soon (the hill).

M.

In article <[email hidden]>, [email hidden] says...

Quoted message said:

brian hughes said:

Most people want to know the average grade for the hill

I want to know the maximum grade which is sustained for any distance of more than ten yards or so.

If that is the case, the number you are looking for will not be accurately determinable from a topo
map or topographic software.

Though forshortened by the camera, this hairpin turn is close to 20°(36%) at the switchback. The 2
1/2 mile Category 2 climb from the valley to the top rises ~1100' or 8% grade.

clee.orgimage022.htmOpen ↗

Do you really want to know??? Which is more difficult? the 2 1/2 miles or this 10m section? I can
climb this 10m section. I could not do it after the previous 2 miles or the 67 miles of climbing
that preceeded that.

--

Cletus D. Lee Bacchetta Giro Lightning Voyager clee.orgclee.orgOpen ↗
- Bellaire, TX USA -

Cletus Lee said:

Which is more difficult? the 2 1/2 miles or this 10m section?

If I know about the 10m section I can fit the lower geared cassette ;-)

But I know what you mean.

Guy
===
** WARNING ** This posting may contain traces of irony. chapmancentral.comchapmancentral.comOpen ↗ Advance
notice: ADSL service in process of transfer to a new ISP. Obviously there will be a week of downtime
between the engineer removing the BT service and the same engineer connecting the same equipment on
the same line in the same exchange and billing it to the new ISP.