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Tips, Tools, Information

Visual Line of Sight

How does one calculate a visual line of sight for objects at a given height that are distant enough that the Earth's curvature needs to be considered?

Visual Line of Sight Calculations dependent on Earth's Curvature

Measuring lens field of view on topographic maps

On the below page I explain how to use simple trigonometry with topographic maps to evaluate what elements in landscapes may be within the field of view of given photographic lenses.

Calculating Photographic Subject Field of Views in Landscapes

Calculating route verticals on USGS topographic maps

Basics using a spreadsheet for calculating route verticals from USGS topographic Maps for hiking and backpacking.

Calculating route verticals from USGS topographic Maps

Not Becoming a Victim of Common Cold Viruses

Non photography advice about avoiding being infected by the Common Cold virus:

Not Becoming a Victim of Common Cold Viruses

100 ASA EV Chart

This is a lens EV, exposure value, chart set for ISO 100 speed film. Of use to large format photographers. Meant to be used in conjunction with a light exposure meter that can read out directly in EV values. The chart size is small in order to be able to be glued onto small areas of equipment like a tripod leg, camera body etc in order to be able to select lens shutter speed and aperture. To copy the chart as a jpg image, Mouse right button click image then Save Picture As to download.


USGS topographic map slope pitch charts

These two small charts relate in map inches, USGS topographic map slope steepness also known as pitch between vertical map lines. To make best use of the chart in order to measure small map distances, one will probably need to use a low power reading magnifier and a good ruler graduated in 100th of an inch lines. There are two charts as USGS topographic maps have both light brown 40 foot and dark brown 200 foot intervals with 4 light brown lines between each darker brown line. A few maps are metric with 20 meter light brown and 100 meter dark brown lines. As an example of use, if there is a half inch map distance between dark brown lines, then the percent grade slope is about 20% that is 11.3 degrees.

Pitch is shown in grade and in degrees. Grade, more properly termed percent grade is a engineering term for vertical rise over horizontal distance. Thus a slope that rises 100 feet in height over 100 feet horizontally has a grade of 100/100 = 1.0 that in percentage is 100%. That is also equal to 45 degrees. A vertical slope of 90 degrees has no distance thus has a grade of infinity. A 60% grade slope or one with a 60 foot rise over 100 feet is a very steep slope to walk up and anything steeper will increasingly result in use of hands. Additionally a snow skier falling on a 60% grade slope unless they immediately self arrest is likely to take a long slide to the bottom of a slope.To copy the chart as a jpg image, Mouse right button click image then Save Picture As to download.


OTA television antenna information for Campbell, CA

For those who live in Campbell, California and don't subscribe to cable TV and instead use an Off The Air aka OTA antenna to directly receive broadcast television signals from San Francisco Bay Area regional television transmitter sites, the following linked page provides information on receiving area signals.
Campbell OTA

   David Senesac

10:32 AM 9/7/2015