How do I save to an array multiple different lat, long pairs?

This is with the intention to save them to storage and use them to draw a track. I know how to save one thing to an array e.g.

pairs = [lat,lon] but ideally I want this array to expand as you save each pair. Pairs = [lat1, lon1, lat2, lon2, lat3, lon3…….]

I have currently got it so onTap returns my current lat and lon.

var pos = Position.getInfo().position;

pos = pos.toDegrees();

lat = pos[0];
lon = pos[1];
pairs = [lat,lon];

Application.Storage.setValue(“points”, pairs);

Help is much appreciated

0 Shent-Aurkhan (SHN) over 4 years ago

so, you want to save/store data everytime onTap?

you could do something like this:

var pair = Application.Storage.getValue(“points”);
if(pair==null){pair = new [0];}

var pos = Position.getInfo().position;
pos = pos.toDegrees();

lat = pos[0];
lon = pos[1];
pair.add(lat);pair.add(lon)

Application.Storage.setValue(“points”, pair);

or for a better readability, something like this:

var pair = Application.Storage.getValue(“points”);
if(pair==null){pair = new [0];}

var pos = Position.getInfo().position;
pos = pos.toDegrees();

lat = pos[0];
lon = pos[1];
var CurrPair = [lat,lon];
pair.add(CurrPair)

Application.Storage.setValue(“points”, pair);

with this, points[0] = 1st pair array, points[1] = 2nd pair array etc

0 Scarecrow123 over 4 years ago in reply to Shent-Aurkhan (SHN)

Thankyou very much! I’ll insert it later when I have some time, i’ll let you know if it works or if I get any errors etc.

0 Scarecrow123 over 4 years ago in reply to Shent-Aurkhan (SHN)

Ok so it works but theres a slight oddity. (I used your first chunk of code)

Instead of this

[lat1, lon1, lat2, lon2, lat3, lat3, lat4, lon4, lat5, lon5] etc

I get this

[lat1, lon1, [lat2, lon2], lat3, lat3, lat4, lon4, lat5, lon5] etc

There’s an extra pair of brackets. Why would that happen?

0 jim_m_58 over 4 years ago in reply to Scarecrow123

It's because of this:

var CurrPair = [lat,lon];
pair.add(CurrPair)

You are doing the add() of an array.

you want to do

pair.add(lat);

pair.add(lon);

0 Scarecrow123 over 4 years ago in reply to jim_m_58

Gotcha, on a side but related note do you have any idea why I might be getting an array out of bounds failed invoking symbol error when attempting to draw those points? The problem occurs at 22.

Me = [240/2, 240/2];

function transformCoordinates(lat, lon){
var pixelsLong = (120 - lon) * (4 / screenWidthPixels);

var pixelsHeight = (lat - 120) * (4 / screenHeightPixels);

var x = Me[0] - pixelsLong;
var y = Me[1] - pixelsLat;

return [x,y];}

function onUpdate;

if (track! = null){

dc.setColor(Graphics.COLOR_BLACK, Graphics.COLOR_TRANSPARENT);

for(var i=0; i < track.size(); i=i+2){
var pointA = transformCoordinates(track[i], track[i+1]);

var pointB = transformCoordinates(track[i+2], track[i+3]);

dc.setPenWidth(8);

dc.drawPoint(pointA[0], pointA[1]);

dc.setPenWidth(3);

dc.drawLine(pointA[0], pointA[1] , pointB[0], pointB[1] );

0 jim_m_58 over 4 years ago in reply to Scarecrow123

In the forloop i<track.size, but in your code you have

var pointA = transformCoordinates(track[i], track[i+1]);

var pointB = transformCoordinates(track[i+2], track[i+3]);

where I+1 i+2 and i+3 will be larger than the size in the last loop.

0 Scarecrow123 over 4 years ago in reply to jim_m_58

So should I make them all just i?

0 jim_m_58 over 4 years ago in reply to Scarecrow123

i is the max size of the array. To loop though the lat/lon pairs,

for(i=0;i<track.size();i=i+2) {
    thisLat=track[i];
    thisLon=track[i+1];
    //do whatever
}

0 Scarecrow123 over 4 years ago in reply to jim_m_58

so my code should be something like this:

for(var i=0; i<track.size();i=i+2){

pointA=track[i];

pointB=track[i+1]

draw point a and point b, that will draw all the points in the track yes?

0 Scarecrow123 over 4 years ago in reply to jim_m_58

I got it to draw the first point.
somehow all the other points have to be drawn as well