What Are Grid Fields and Squares?

What are “Fields” and what are “Squares”?

As you have likely guessed, we are referring to the “Maidenhead Locator System”. Please be patient, the reason we begin this explanation should become clear shortly.

The earth is divided into a grid of rectangles called “Fields”. Grid fields are 10 degrees of latitude “high” by 20 degrees of longitude “wide”. Thus each field is about 1,609 km by about 1,126 km (1000 miles by 700 miles) in size. There are 18 rows and 18 columns of grid fields - for a total of 324.

Each grid field is further divided into 100 “Squares”. Grid squares are 1/100 the size of a field - about 160 km by 112 km (100 miles wide by 70 miles high). Each grid field holds 10 rows and 10 columns, or 100 grid squares. Covering our map of the world there are 324 grid fields times 100 squares in each for a total of 32,400 grid squares.

Why did we go there?

The Coverage-Analysis View provides predictions for grid “Fields” or grid “Squares”. Why both? It is a lot quicker to predict and display the information for each of 324 grid fields than it is for 32,400 grid squares. Don’t forget, for a complete prediction, we must create a prediction for “each field” or “each square” for “each” of the 24 hours in our day. In addition we must do so for each desired frequency in our "frequency set".

Just for info here are one more set of numbers. For an entire day, or “group”, of "one single frequency" predictions – using grid fields we generate 7,776 “location hours”; using grid squares we generate 100 times more, or 777,600 location hours. These are impressive numbers aren’t they? These prediction sets can result in a huge amount of data. No worry, WinCAP Wizard will (almost) effortlessly manage all of that prediction data.

The user doesn’t actually need to know all this but it might make things easier to understand. Plus it could be useful knowledge. It should also help explain why a grid square prediction set takes so long to create.

Why is WinCAP Wizard, or VOACAP, so slow?

Lets do a bit of quick investigation. Below are timings for predictions on the P3 1 GHz machine used to develop WinCAP Wizard.

Lets discuss timings for a set of "grid square" predictions. Recall, with a set of "grid square" predictions, we are discussing 32,400 location predictions multiplied by 24 hours multiplied by the number of frequencies. We have large numbers in a hurry. There isn't much sense in discussing single hour predictions, as they aren't very useful for our purpose.

VOACAP takes about 32 minutes (1920 seconds) for each frequency set (1 frequency for each of 24 hours); again on a P3 1 GHz machine.

Now lets examine these 1920 seconds more closely:

1920 (seconds) / 24 (hours) = 80 seconds each hour-frequency

1920 (seconds) / 32,400 (grid squares) = 0.06 seconds per each of these (32,400) predictions.

WinCAP Wizard requires about 1 minute to parse and store each of these frequency sets.

For grid fields:

VOACAP takes about 21.6 seconds for each frequency set (1 frequency for each of 24 hours); again on a P3 1 GHz machine. Again, about 0.06 seconds for each target, grid field, prediction. The parse and store time is less than one second.

Some users may recall running the early version of IonCAP (perhaps version PC.31) on an IBM PC and measuring the time required to create "one" prediction for "one" circuit in "hours".

Conclusions --

VOACAP is extremely fast, but please be patient. If you are in a hurry, and perhaps for general use, do grid field predictions.