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Allow arbitrary HGT grid sizes

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This commit is contained in:
Martin Tůma 2024-02-27 21:13:12 +01:00
parent 2026036015
commit c33215565f
2 changed files with 60 additions and 45 deletions
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87
src/common/dem.cpp
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@ -20,12 +20,16 @@
#include "rectc.h"
#include "dem.h"
#define SRTM3_SAMPLES 1201
#define SRTM1_SAMPLES 3601
#define SRTM05_SAMPLES 7201
#define SRTM_SIZE(samples) \
((samples) * (samples) * 2)
static unsigned int isqrt(unsigned int x)
{
unsigned int r = 0;
while ((r + 1) * (r + 1) <= x)
r++;
return r;
}
static double interpolate(double dx, double dy, double p0, double p1, double p2,
double p3)
@ -34,42 +38,21 @@ static double interpolate(double dx, double dy, double p0, double p1, double p2,
+ p2 * dy * (1.0 - dx) + p3 * dx * dy;
}
static double value(int col, int row, int samples, const QByteArray *data)
static double value(int col, int row, int samples, const QByteArray &data)
{
int pos = ((samples - 1 - row) * samples + col) * 2;
qint16 val = qFromBigEndian(*((const qint16*)(data->constData() + pos)));
qint16 val = qFromBigEndian(*((const qint16*)(data.constData() + pos)));
return (val == -32768) ? NAN : val;
}
static double height(const Coordinates &c, const QByteArray *data)
{
int samples;
if (data->size() == SRTM_SIZE(SRTM3_SAMPLES))
samples = SRTM3_SAMPLES;
else if (data->size() == SRTM_SIZE(SRTM1_SAMPLES))
samples = SRTM1_SAMPLES;
else if (data->size() == SRTM_SIZE(SRTM05_SAMPLES))
samples = SRTM05_SAMPLES;
else
return NAN;
double lat = (c.lat() - floor(c.lat())) * (samples - 1);
double lon = (c.lon() - floor(c.lon())) * (samples - 1);
int row = (int)lat;
int col = (int)lon;
double p0 = value(col, row, samples, data);
double p1 = value(col + 1, row, samples, data);
double p2 = value(col, row + 1, samples, data);
double p3 = value(col + 1, row + 1, samples, data);
return interpolate(lon - col, lat - row, p0, p1, p2, p3);
}
QMutex DEM::_lock;
DEM::Entry::Entry(const QByteArray &data) : _data(data)
{
_samples = isqrt(_data.size() / 2);
}
QString DEM::Tile::latStr() const
{
const char ns = (_lat >= 0) ? 'N' : 'S';
@ -105,7 +88,25 @@ void DEM::clearCache()
_data.clear();
}
QByteArray *DEM::loadTile(const Tile &tile)
double DEM::height(const Coordinates &c, const Entry *e)
{
if (!e->samples())
return NAN;
double lat = (c.lat() - floor(c.lat())) * (e->samples() - 1);
double lon = (c.lon() - floor(c.lon())) * (e->samples() - 1);
int row = (int)lat;
int col = (int)lon;
double p0 = value(col, row, e->samples(), e->data());
double p1 = value(col + 1, row, e->samples(), e->data());
double p2 = value(col, row + 1, e->samples(), e->data());
double p3 = value(col + 1, row + 1, e->samples(), e->data());
return interpolate(lon - col, lat - row, p0, p1, p2, p3);
}
DEM::Entry *DEM::loadTile(const Tile &tile)
{
QString bn(tile.baseName());
QString fn(QDir(_dir).absoluteFilePath(bn));
@ -113,15 +114,15 @@ QByteArray *DEM::loadTile(const Tile &tile)
if (QFileInfo::exists(zn)) {
QZipReader zip(zn, QIODevice::ReadOnly);
return new QByteArray(zip.fileData(bn));
return new Entry(zip.fileData(bn));
} else {
QFile file(fn);
if (!file.open(QIODevice::ReadOnly)) {
qWarning("%s: %s", qPrintable(file.fileName()),
qPrintable(file.errorString()));
return new QByteArray();
return new Entry();
} else
return new QByteArray(file.readAll());
return new Entry(file.readAll());
}
}
@ -131,15 +132,15 @@ double DEM::elevation(const Coordinates &c)
return NAN;
Tile tile(floor(c.lon()), floor(c.lat()));
QByteArray *ba = _data.object(tile);
Entry *e = _data.object(tile);
double ele;
if (!ba) {
ba = loadTile(tile);
ele = height(c, ba);
_data.insert(tile, ba, ba->size());
if (!e) {
e = loadTile(tile);
ele = height(c, e);
_data.insert(tile, e, e->data().size());
} else
ele = height(c, ba);
ele = height(c, e);
return ele;
}

18
src/common/dem.h
View File

@ -44,9 +44,23 @@ public:
static QList<Area> tiles();
private:
typedef QCache<DEM::Tile, QByteArray> TileCache;
class Entry {
public:
Entry() : _samples(0) {}
Entry(const QByteArray &data);
static QByteArray *loadTile(const Tile &tile);
const QByteArray &data() const {return _data;}
int samples() const {return _samples;}
private:
unsigned int _samples;
QByteArray _data;
};
typedef QCache<DEM::Tile, Entry> TileCache;
static double height(const Coordinates &c, const Entry *e);
static Entry *loadTile(const Tile &tile);
static QString _dir;
static TileCache _data;