That’s actually a really good question. I wonder…

Gosh, my whole state is covered in blue/green.

    assert((w == 1236) && (h == 1165));
    MercatorAspectRatio = float(w)/float(h);
    EquatorY = float(h-565)/float(h);
    MeridianX = float(618)/float(w);
    LatScale = (float(h-456)/float(h) - EquatorY)/0.549306144335f;   // 30 degrees
    LonScale = 1-MeridianX;

or this:

vector_2 XYFromLatLon( float lat, float lon )
{
    float x = MeridianX + LonScale*(lon/180.0);
    lat = RadiansFrom(lat);
    float y = EquatorY + LatScale*log((sin(lat) + 1)/cos(lat));
    // return vector_2(WindowWidth*x,(WindowWidth/MercatorAspectRatio)*y);
    return vector_2(MercatorAspectRatio*x,y);
}

and this:

    glBindTexture(GL_TEXTURE_2D,BlobTexId);
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glBegin(GL_QUADS);
    for(uint i = 0, ni = IPAddresses.size(); i < ni; ++i) {
        uint ip = IPAddresses[i];
        geo_ip_range* range = FindIPRange(ip);
        if(!range) {
            continue;
        }
        geo_location* loc = FindLocation(range->locid);  assert(loc);
        float r = 0.007f, a = 0.15;
        vector_3 green = RGBtoHSV(vector_3(0.0f,1.0f,0.0f));
        vector_3 blue = RGBtoHSV(vector_3(0.0f,0.0f,1.0f));
        float t = float(i)/float(ni);
        vector_3 c = HSVtoRGB(t*green + (1-t)*blue);
        glColor4f(c.x,c.y,c.z,a);

        vector_2 xy = XYFromLatLon(loc->lat,loc->lon) + r*vector_2(genrand_real_cc()-0.5f,genrand_real_cc()-0.5f);
        float z = i*1e-7f;
        glTexCoord2f(0,0); glVertex3fv(make_v3(xy-vector_2(-r,-r),z).el);
        glTexCoord2f(1,0); glVertex3fv(make_v3(xy-vector_2( r,-r),z).el);
        glTexCoord2f(1,1); glVertex3fv(make_v3(xy-vector_2( r, r),z).el);
        glTexCoord2f(0,1); glVertex3fv(make_v3(xy-vector_2(-r, r),z).el);
    }
    glEnd();

Etc. Basically, I downloaded the geolocation csv files and map I mention above, figured out where the important parts of the map were in the image, load it in, render it as a texture, then look up all the IPs and splat them down as a little gaussian alpha blob texture.

What did you use to render the map, if you’d care to give a short comment?