Making the Projection

The straightforward 6-step transition of point T from the Plan and Side views on the worksheet to its perspective coordinates X and Y is shown in Fig. 3. The transfer of X and Y to the picture plane is shown in Fig. 4. This procedure is typical for all points required to complete the projection.

Fig. 3 — Illustrating the five steps for translating a typical point (T) from the
Plan and Side views into its X Y picture plane coordinates.

1. From the Plan View (in the Horizontal Plane) drop point T via line 1 into the Profile Plane.
2. Translate point T from the Side View (or Front View, whichever is more suitable) via line 2 to intersect line 1 at T1.
3. Let the line of sight, line 3, extend from EP through T1 to pierce the Picture Plane at T2.
   The dimension Y (between LOS and T2) is the elevation coordinate for the perspective
   of point T.
4. Translate T2 via line 4 into the Horizontal Plane.
5. Let line 5 extend from EP through T to intersect line 4 at T3.
   The dimension X (between PLOS and T3) is the azimuth coordinate for the perspective
   of point T.
6. Measure and transfer the X and Y coordinates from steps 3 and 5 to the picture plane grid. See Fig. 4.

Fig. 5 — The completed projection made from the 3-view (Fig. 8.) The grid marks on the X-Y axes are at 1-inch intervals to assist in plotting.

Notes:

• The image produced by the 6-step procedure makes a drawing 1-to-1 size with the 3-view—in the example, it’s about 6 inches wide. To make a larger image directly on the Picture Plane without the necessity of photocopying or other means of enlargement, multiply each X-Y coordinate pair by an enlargement factor and plot the points on an appropriately sized grid. E.g., to make a 12-inch image, use an enlargement factor of 2.
  
• No matter the viewing aspect of the airplane (object) the basic format arrangement of the worksheet remains unchanged; note the following characteristics in Fig. 6 and Fig. 7.
  • Baseline (BL) is parallel to the Plan View Line of Sight (PLOS.)
  • The Center of Vision (CV) on both BL and PLOS are in vertical alignment perpendicular to PLOS.
  • The Picture Plane (PP) has a constant right angle relationship with the Line of Sight (LOS),
    regardless of the Elevation angle.
  • The Viewing Distance (Dist) is measured between the Eye Position (EP) and the Center of Vision
    (CV) on the Line of sight (LOS.)
  • Eye Position (EP) on PLOS is in vertical alignment with EP on LOS.
• In the 6-steps described in MAKING THE PROJECTION, lines were used to show the origin, direction and termination points of lines 1 through 5. Obviously, if you were to draw those lines for every point required to make the perspective (ref: Fig. 3) the layout would soon become hopelessly cluttered. Actually, tick marks (+)at points T1, T2 and T3 will suffice.
• The direction of transfer of points between the Horizontal Plane and the Profile plane via lines (1) and (4) must be parallel to the vertical line. Similarly, points transferred from the Side and/or Front view via line (2) must be parallel to the base line. This is usually done using the “Triangle and T-Square” method. A less awkward method is to use a ruler or dividers to measure the distance of the points T and T2 from the vertical line and transfer those dimensions to points T1 and T3. Similarly, measure the distance of point T in the Side and/or Front View from the baseline for transfer to point T1.