我想用Matlab对卫星轨迹图进行颜色编码

Question

我在Matlab中创建了一个绘图，用于绘制几颗GPS卫星的方位角和高度。下面是绘制的GPS卫星轨迹图像的示例。

但是，我还想在同一个图上绘制S_4指数（由电离层引起的闪烁效应）。我想对每个GPS卫星路径进行颜色编码，以将高S_4索引显示为红色，将低S_4索引显示为蓝色。我有所有这些的数据，但我无法找到一种方法来对每个GPS路径进行颜色编码。

目前我知道每个卫星在每一天的位置（这就是我能够绘制轨迹的方式）。我在不同的时间和不同的卫星上也有S_4个索引值（S_4索引矩阵与卫星位置矩阵的大小不同）。

有什么想法吗？

这是我使用的功能。它使用一个名为plotMat的矩阵作为输入：

plotMat=[svID(satellite id number), gpsSec, elevation(radians), azimuth(radians)]

我的功能：

% find out from 'plotMat' if plotting satellite locations or trajectories in
% addition determine how many satellites are being tracked and how many
% samples for each satellite (# samples / satellite must always be equal)
gpsTime = plotMat(1,2);
i = 1;
t = gpsTime;
while ((i ~= size(plotMat,1)) & (t == gpsTime))
  i = i + 1;
  t = plotMat(i,2);
end
if (t == gpsTime)
  sats = i;
else
  sats = i - 1;
end;
samples = size(plotMat,1) / sats;
SVs = plotMat(1:sats,1);
elevation = plotMat(:,3);
azimuth = plotMat(:,4);
% initialize polar - plotting area
figure(10);clf;
axis([-1.4 1.4 -1.1 1.1]);
axis('off');
axis(axis);
hold on;
% plot circular axis and labels
th = 0:pi/50:2*pi;
x = [ cos(th) .67.*cos(th) .33.*cos(th) ];
y = [ sin(th) .67.*sin(th) .33.*sin(th) ];
plot(x,y,'color','w');
text(1.1,0,'90','horizontalalignment','center');
text(0,1.1,'0','horizontalalignment','center');
text(-1.1,0,'270','horizontalalignment','center');
text(0,-1.1,'180','horizontalalignment','center'); 
% plot spoke axis and labels
th = (1:6)*2*pi/12;
x = [ -cos(th); cos(th) ];
y = [ -sin(th); sin(th) ];
plot(x,y,'color','w');
text(-.46,.93,'0','horizontalalignment','center');
text(-.30,.66,'30','horizontalalignment','center');
text(-.13,.36,'60','horizontalalignment','center');
text(.04,.07,'90','horizontalalignment','center');
% plot titles
if (samples == 1)
  title('Satellite Position Plot');
  subtitle = sprintf('GPS time : %.2f sec',plotMat(1,2));
else
  title('Satellite Trajectory Plot');
  subtitle = sprintf('GPS time range : %.2f sec to %.2f sec', ...
                     plotMat(1,2),plotMat(size(plotMat,1),2));
  text(-1.6,1,'SVID/Last Position','color','r');
  text(-1.6,.9,'Positive Elevation','color','y');
  text(-1.6,.8,'Negative Elevation','color','b');
end
text(0,-1.3,subtitle,'horizontalalignment','center');
% plot trajectories (or positions) and label the last postion with the
% satellite SV id; in addition, last postions are in red, otherwise position
% elevations are yellow and negative elavations are blue
%
% loop through samples
for s = 1:samples       
  % plot each satellite location for that sample
  for sv = 1:sats
    % check if positive or negative elevation
    if (elevation((s - 1) * sats + sv) < 0)
      elNeg = 1;
    else
      elNeg = 0;
    end
    % convert to plottable cartesian coordinates
    el = elevation((s - 1) * sats + sv);
    az = azimuth((s - 1) * sats + sv);
    x = (pi/2-abs(el))/(pi/2).*cos(az-pi/2);
    y = -1*(pi/2-abs(el))/(pi/2).*sin(az-pi/2);
    % check for final sample
    if (s == samples)
      plot(x,y,'r*');
      text(x,y+.07,int2str(SVs(sv)), ...
           'horizontalalignment', ...
           'center','color','r');
    else
      % check for +/- elevation
      if (elNeg == 0)
        plot(x,y,'y.');
      else
        plot(x,y,'b.');
      end
    end
  end
end

axis equal;

在前面的代码中，我没有添加S_4索引。以下代码将闪烁（S_4）数据的GPS秒与GPS秒与卫星位置数据进行比较。矩阵scint.mat指的是闪烁数据，而txinfo.mat指的是卫星位置数据。此代码创建的组合代码与GPS秒和卫星识别号码一致。

load('scint_324_first')
scint = scint';

load('txinfo_324_first_wrw')
txinfo = txinfo';

k = 0;

for i = 1:length(scint)
    disp(num2str(i))
    for j = 1:length(txinfo)
        if scint(i,2) == txinfo(j,2) && scint(i,15) == txinfo(j,8)
            k = k+1;
            combo(k,:) = [scint(i,:) txinfo(j,:)];
        end
    end
end

Answer 1

如果S_4值随时间变化，颜色编码是否会在单行内发生变化？

它可能不是最有效的方式，但你可以为每一条轨道绘制线条。喜欢

s4code = [1 0 0; 0 0 1]; % blue & red 

for i = time_vector
 if s4(i) > something
  s = 2
 else 
  s = 1
 end
 line(x(i:(i+1)), y(i:(i+1)), 'color', s4code(s, :))
end

关于轨道数据和s4数据不具有相同的大小...使它们具有相同的大小...例如interp1 ;-)

Answer 2

如果您使用极坐标绘图，请尝试3D Polar Plot（Ken Garrard的FEX代码）

如果您使用plot，请尝试Colored line or scatter plot或cline.m（再次使用FEX文件）

最后一个情节是通过以下方式完成的：

x = 1:300
color_line(x,sin(x/20),sin(x/20))