POINTS AFFECTING THE APPEARANCE OF OBJECTS AT DIFFERENT DIST

[SeekHer]

POINTS AFFECTING THE APPEARANCE OF OBJECTS AT DIFFERENT DISTANCES

From: United States Army. Field Service Pocket Book (1917); page 98-99

An object appears nearer:
When looking over a body of water, snow, or level plain or a large ravine or depression
When the sun is behind the observer or if the object is in the bright light
When the air is clear, especially after a rain
When in high altitudes and very clear atmosphere.
When below the observer.
When the background is in contrast with the color of the object

An Object appears more distant:
When looking over rolling country
When the sun is in front of the observer
When the air is not clear, due to fog, smoke, rain, etc.
When up a steep hill from the observer
When the background is similar in color to that of the object.

On hot days, especially when the ground is moist, an object will appear more distant if observed from a kneeling or sitting position. This is due to refraction and heat radiation. Sometimes this refraction renders the object invisible.

The Tendency is to underestimate:
When using field glasses.
When trees are leafless--as is winter.
When the trees or branches are silhouetted against a clear skyline or a contrasting background.

Objects are distinguishable to average eyes at the following distances:
9 to 12 miles, church spires
5 to 7 miles, windmills
2 to 2-1/2 miles, chimneys
2,000 yards, trunks of large trees
600 yards, individuals of a column
500 yards, individual panes of glass in windows
400 yards, arms and legs of dismounted men



DISTANCE ESTIMATION BY THE APPEARANCE OF TREES

The following table is a method for estimating distance by the appearance of tree trunks, their branches and foliage (using the naked eye).

Distance......Trunk......Main or Inner Minor or outer......Remarks
........._________________branches_____branches

500 to
1000 yds.......Visible......Visible......Visible......
The foliage pertaining to each branch toward the observer can be easily distinguished.

1000 to
1500 yds.......Visible......Visible......Distinguishable
The foliage begins to blend in cluster-like shape, but does not appear so dense but that some of the larger branches can be seen through it. With the sky as a background daylight can be seen through the foliage.

1500 to
2000 yds.......Visible......Visible......Blending with or obscured by the foliage
The foliage is more densely clustered, presenting a rough surface. The outlines of the foliage of a large branch or group of branches are distinguishable.

2000 to
2500 yds.......Visible......Distinguishable......Blending with or obscured by the foliage
The foliage is in clusters appearing as a smooth surface. The outlines of the foliage of separate trees distinguishable.

2500 to
3000 yds.......Visible......Distinguishable......Blending with or obscured by the foliage
The foliage assumes the appearance of a continuous cluster blending with the foliage of adjoining trees.

3000 to
3500 yds.......Lower half Visible......Blends with foliage......Blending with or obscured by the foliage
The foliage assumes the appearance of a continuous cluster blending with the foliage of adjoining trees.

3500 to
4000 yds.......Lower half distinguishable......Blends with foliage......Blending with or obscured by the foliage
The foliage assumes the appearance of a continuous cluster blending with the foliage of adjoining trees.

4000 to
5000 yds.......Blending with foliage......Blends with foliage......Blending with or obscured by the foliage
Surface of each cluster or group of clusters, smooth; motion caused by ordinary winds cannot be detected.

5000 yards and beyond the whole area covered by trees appears like a bushy area at about 1000 yards, except that the surface is smoother and blacker.