GB2192063A

GB2192063A - Interpolation device for graphical coordinate values

Info

Publication number: GB2192063A
Application number: GB08615890A
Authority: GB
Inventors: John Robert Rimmer
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1986-06-30
Filing date: 1986-06-30
Publication date: 1987-12-31
Also published as: DE8708589U1; GB8615890D0; FR2600792B3; FR2600792A3

Abstract

A device for aiding interpolation of coordinate values on graphs and the like comprises a transparent baseplate (30) marked with an interpolation scale (6) and provided with a cursor-line (42) on a transparent cursor (34) slideable on the baseplate (30) over the interpolation scale. The interpolation scale (6) comprises a baseline (8), which can be aligned with one of the axes of the graph by superimposing it over a suitable graph gridline (40), and an array of scale lines (9) radiating from a common origin on the baseline (8) at acute angles to it but with equal spacing between themselves at right angles to the baseline. Appropriate sub-divisions for interpolation of the intervals between the graph gridlines (40,44) are defined by positioning the cursor line (42) over the interpolation scale (6) so that the cursor line (42) intersects the point (43) where, e.g. the outermost one of the scale lines (9) passes through the graph gridline (44) next above the baseline (8). The point X on the graph (45) can then be interpolated between grid lines (40,44). <IMAGE>

Description

SPECIFICATION Interpolation device for graphical coordinate values This invention relates to a device for aiding interpolation of coordinate values on graphs.

When reading values from a graph which has been plotted over widely spaced grid lines, it is difficult to interpolate values between the grid lines with any great degree of accuracy. The present invention enables a finer scale to be easily defined for any size of grid, and therefore allows points on the graph to be interpolated more accurately.

According to the present invention a device for aiding interpolation of coordinate values on graphs and the like comprises a base plate, at least a portion of which is constituted by a transparent material having an interpolation scale marked thereon, and a cursor slidable on the base plate over the interpolation scale, at least a portion of which cursor is constituted by a transparent material having a cursor line marked thereon, the interpolation scale comprising a base line for alignment with one of the axes of the graph, and an array of scale lines radiating from a common origin on the base line at acute angles thereto, the arrangement being such that when the cursor line is positioned over the interpolation scale, the cursor line intersects the base line at right angles and the scale lines intersect the cursor line at equispaced points therealong.

It is advantageous if the base plate and/or the cursor are constructed substantially wholly of a transparent material such as polymethyl methacrylate.

It is further convenient if the interpolator scale comprises ten scale lines as well as the base line. The base plate may also have lines marked thereon to define commonly used graph grid sizes.

It may be advantageous if the cursor is constructed such as to magnify the area viewed therethrough, and preferably the cursor is also detachable from the base plate.

It would be within the scope of the present invention if merely the interpolator grid portion of the base plate were to be transparent, the rest of the base plate being opaque. When the word "transparent" is used in the present specification it should be taken to include translucent within its meaning, provided of course that the degree of transparency is such that when the device is placed upon a graph to be read the graph grid and the graph plot can be seen sufficiently clearly.

The construction and operation of embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows enlarged plan, side and end views of an interpolation device according to the present invention; Figure 2a is a diagrammatic plan view of a further embodiment of the invention being utilised to interpolate a point on a graph; and Figure 2b is an enlarged view on section B B in Figure 2a.

Referring to Figure 1, an interpolator device 1 comprises two basic components, namely a transparent base plate 2 and a slidable transparent cursor 4.

An interpolation scale 6 is engraved or otherwise marked on the base plate, and comprises a base line 8 and an array of ten scale lines 9, which radiate from a common origin on the base line at acute angles to it.

The slidable cursor 4 is provided with a cursor line 10 which, when the cursor is positioned over the interpolation scale, intersects the base line 8 at right angles. The spacing between the scale lines 9 is such that the scale lines intersect the cursor line 10 at equally spaced points along it. Also marked on the base plate 2 are lines 11,12 and 13 which intersect the base line 8 at right angles.

Line indicates the origin of the scale lines 9.

The distance along lines 12 and 13 between the base line 8 and the outermost of the scale lines 9 are respectively one centimetre and one inch and represent commonly used graph grid sizes. The lines 11,12 and 13 are for convenience only and do not constitute part of the invention.

The cursor 4 slides in channels 16,17 provided at the sides of the base plate 2. In order to provide the cursor 4 with a good sliding action in the channels 16, one end of the cursor is formed to accept a wavy spring 18 having two spaced apart major corrugations which engage the side 20 of the channel 16 in which that end of the cursor slides. To avoid abrasion between the interpolation scale 6 and cursor 4, a clearance 20 is provided between the main portion of the cursor 4 and the main portion of the base plate 2. This clearance 20 is achieved by provision of the small lands 22 and 23 in the channels 16 and 1 7. The cursor 4 can be pushed past the detents 26 at each end of the channel 16 in order to remove it for cleaning if desired.

In Figure 1 the interpolator device is shown at greater than full size for this particular embodiment, however the size of the device is obviously at the discretion of the designer according to the market for which he is designing.

Referring now to Figure 2a, there is shown another embodiment of the device, comprising a plane transparent base plate 30 provided with grooves 32 in its side edges. Inturned ends 33 of the cursor 34 wrap around the top edges of the grooves 32 and slide in them as shown in Figure 2b. A clearance 36 similar to clearance 20 in Figure 1 can be easily achieved in the present embodiment by appropriate dimensioning of the cursor 34. A good sliding action for the cursor 34 can be readily achieved without the use of a separate spring acting between the cursor and the base plate 30 if the gap between the two inturned ends 33 of the cursor 34 is made slightly smaller than the distance separating the two grooves 32 in the side edges of the base plate 30.

The mode of use of the interpolator device shown in Figure 2 will now be described. The device shown in Figure 1 is of course used in the same way.

To use the interpolator device on any selected graph, the interpolator device is placed on top of the graph with the base line 8 of the interpolator scale 6 superimposed over a suitable grid line 40 of the graph. The cursor 34 is then moved so that the cursor line 42 marks a position 43 where the top one of the scale lines 9 crosses the graph grid line 44 next above the grid line 40. This now defines a scale which sub-divides the spaces between the graph grid lines into ten equal portions.

To interpolate any point on the graph plot 45, the interpolator device is positioned over the graph plot with the base line 8 of the interpolator 6 lying on the graph grid line 40 immedi mately bellow the point x on the graph plot which is to be evaluated by interpolation, and with the cursor line lying on the point x. The value of the point x, in this case its value on the ordinate or vertical scale, can now be read off.

In the embodiments shown in Figures 1 and 2 the interpolator scales 6 consist of a base line 8 and ten scale lines 9, but of course different numbers of scale lines can be utilised if desired to define any convenient number of sub-divisions for the graph grids of the graph plots to be evaluated. However, the interpolator devices as shown can equally well be utilised if the graph has an unusual scale, for example seven units per grid space. In this case then the procedure described above is used to define the sub-scale, except that the cursor line 42 would be moved to lie over the point where the seventh scale line above the base line 8 crossed the next grid line, and hence each sub-division on the cursor line between the two graph grid lines would be of one unit.

Various refinements of the device may be made without departing from the scope of the invention. For instance the cursor 34 (Figure 2) or 4 (Figure 1) may be provided with a convex top surface so that it magnifies the area viewed through it. Other variations in design and use of interpolator devices according to the invention may be envisaged by the specialist.

Claims

1. A device for aiding interpolation of coordinate values on graphs and the like comprising a base plate, at least a portion of which is constituted by a transparent material having an interpolation scale marked thereon, and a cursor slidable on the base plate over the interpolation scale, at least a portion of which cursor is constituted by a transparent material having a cursor line marked thereon, the interpolation scale comprising a base line for alignment with one of the axes of the graph, and an array of scale lines radiating from a common origin on the base line at acute angles thereto, the arrangement being such that when the cursor line is positioned over the interpolation scale, the cursor line intersects the base line at right angles and the scale lines intersect the cursor line at equispaced points therealong.

2. A device according to claim 1 in which the base plate and/or the cursor are constructed substantially wholly of a transparent material.

3. A device according to claim 1 or claim 2 in which the interpolator scale comprises the base line and ten scale lines.

4. A device according to any one of claims 1 to 3 having lines marked on the base plate to define one or more commonly used graph grid sizes.

5. A device according to any one of claims 1 to 4 in which the cursor is constructed so as to magnify the area viewed therethrough.

6. A device substantially as described in this specification with reference to and as illustrated by Figure 1 or Figure 2 of the accompanying drawings.