Trigonometric values

The below sentence can be interpreted to remember the values of sin, cos, and tan. This sentence: (Some People Have. Curly Brown Hairs. Till painted Black).
The sentence: (Some People Have) represents the first letters as SPH interpreted as:
Sin = Perpendicular / Hypotenuse.
The sentence: (Curly Brown Hairs) represents the first letters as CBH interpreted as:
Cos = Base / Hypotenuse.
The sentence: (Till Painted Black) represents the first letters TPB interpreted as:
Tan = Perpendicular / Base.
Thus the sentence: (Some People Have. Curly Brown Hairs. Till painted Black). Helps to remember interpretation of Trigonometric values of Sin, Cos and Tan.

Introduction of photogrammetry

This publication is written by Mr. Manoj Karagudri. In reference to understanding of photogrammetry which is a part of B-TECH or BE in Civil Engineering.
Bitly short url link.

Photogrammetry is one of the surveying concepts of civil engineering to calculate accurate measurements using photographs. Useful in creating maps, soil classification. In terrestrial photogrammetry the photographs are taken from ground. In aerial photogrammetry they are taken from aircrafts. Aerial is preferred better compared to terrestrial. The first attempt for experiment is recorded in 1851.

In terrestrial photogrammetry the instrument phototheodolite, combination of camera and theodolite is used. This technique is similar to plane table surveying. The same object photographed from different directions from the known points on measured base line. The positions of objects can be calculated by interpolation of two rays at the same object.

To cover the entire area several pairs of photographs with parallel camera axis are taken from two known points on the baseline.

Definition terminology

Camera axis is the line passing through the center of camera lens. Perpendicular to the camera plate (negative) and picture plane. It coincides with optical axis.

Here is the link to the YouTube video created by Engineer, Mr. Manoj Karagudri. To help understand the terminology concepts.

Picture plane (positive) is an imaginary plane perpendicular to camera axis located at focal distance in front of the lens.

Principal point is the intersection of camera axis and picture plane (positive) or camera plate (negative).

Focal length (f) is the perpendicular distance from the center of the lens to the picture plane or camera plate. It is defined by f=uv/(u+v) where u is object distance, and v is image distance.

Principal plane: contains optical axis and is perpendicular to camera plate and picture plane.

Fiducial axis: reference lines intersecting at 90 degrees. Refered as x and y axis.

Film base: is a thin, flexible, transparent sheet of cellulose nitrate or cellulose acetate coated with light sensitive emulsion.