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Fix: lat and lon were inverted in tooGeoHash
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@muchembledMartin
muchembledMartin committed Mar 3, 2024
2 parents 84ef58e + dbe750f commit c30e1e5
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Showing 2 changed files with 272 additions and 150 deletions.
248 changes: 165 additions & 83 deletions src/main/java/com/esri/core/geometry/Geohash.java
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Original file line number Diff line number Diff line change
Expand Up @@ -6,94 +6,176 @@
* Helper class to work with geohash
*/
public class Geohash {

private static final String base32 = "0123456789bcdefghjkmnpqrstuvwxyz";

private static final String INVALID_CHARACTER_MESSAGE = "Invalid character in geohash: ";
private static final String GEOHASH_EXCEED_MAX_PRECISION_MESSAGE = "Precision to high in geohash (max 24)";

/**
* Create an evelope from a given geohash
* @param geoHash
* @return The envelope that corresponds to the geohash
* @throws InvalidParameterException if the precision of geoHash is greater than 24 characters
*/
public static Envelope2D geohashToEnvelope(String geoHash){
if(geoHash.length() > 24){
throw new InvalidParameterException(GEOHASH_EXCEED_MAX_PRECISION_MESSAGE);
}

long latBits = 0;
long lonBits = 0;
for(int i=0; i < geoHash.length(); i++){
int pos = base32.indexOf(geoHash.charAt(i));
if(pos == -1){
throw new InvalidParameterException(
new StringBuilder(INVALID_CHARACTER_MESSAGE)
.append('\'')
.append(geoHash.charAt(i))
.append('\'').toString());
}

if(i%2 == 0){
lonBits = (lonBits << 3) | ((pos>>2) & 4) | ((pos>>1) & 2) | (pos & 1);
latBits = (latBits << 2) | ((pos>>2) & 2) | ((pos>>1) & 1);
}else{
latBits = (latBits << 3) | ((pos>>2) & 4) | ((pos>>1) & 2) | (pos & 1);
lonBits = (lonBits << 2) | ((pos>>2) & 2) | ((pos>>1) & 1);
}
}

int lonBitsSize = (int) Math.ceil(geoHash.length()*5/2.0);
int latBitsSize = geoHash.length()*5 - lonBitsSize;

double lat = -90;
double latPrecision = 90;
for(int i = 0; i < latBitsSize; i++){
if(((1 << (latBitsSize-1-i)) & latBits) != 0){
lat += latPrecision;
}
latPrecision /= 2;
}

double lon = -180;
double lonPrecision = 180;
for(int i = 0; i < lonBitsSize; i++){
if(((1 << (lonBitsSize-1-i)) & lonBits) != 0){
lon += lonPrecision;
}
lonPrecision /= 2;
}

return new Envelope2D(lon, lat, lon + lonPrecision*2, lat + latPrecision*2);

private static final String base32 = "0123456789bcdefghjkmnpqrstuvwxyz";

private static final String INVALID_CHARACTER_MESSAGE =
"Invalid character in geohash: ";
private static final String GEOHASH_EXCEED_MAX_PRECISION_MESSAGE =
"Precision to high in geohash (max 24)";

/**
* Create an evelope from a given geohash
* @param geoHash
* @return The envelope that corresponds to the geohash
* @throws InvalidParameterException if the precision of geoHash is greater than 24 characters
*/
public static Envelope2D geohashToEnvelope(String geoHash) {
if (geoHash.length() > 24) {
throw new InvalidParameterException(GEOHASH_EXCEED_MAX_PRECISION_MESSAGE);
}

/**
* Computes the geohash that contains a point at a certain precision
* @param pt A point represented as lat/long pair
* @param characterLength - The precision of the geohash
* @return The geohash of containing pt as a String
*/
public static String toGeohash(Point2D pt, int characterLength){

return "";
long latBits = 0;
long lonBits = 0;
for (int i = 0; i < geoHash.length(); i++) {
int pos = base32.indexOf(geoHash.charAt(i));
if (pos == -1) {
throw new InvalidParameterException(
new StringBuilder(INVALID_CHARACTER_MESSAGE)
.append('\'')
.append(geoHash.charAt(i))
.append('\'')
.toString()
);
}

if (i % 2 == 0) {
lonBits =
(lonBits << 3) | ((pos >> 2) & 4) | ((pos >> 1) & 2) | (pos & 1);
latBits = (latBits << 2) | ((pos >> 2) & 2) | ((pos >> 1) & 1);
} else {
latBits =
(latBits << 3) | ((pos >> 2) & 4) | ((pos >> 1) & 2) | (pos & 1);
lonBits = (lonBits << 2) | ((pos >> 2) & 2) | ((pos >> 1) & 1);
}
}

/**
* Compute the longest geohash that contains the envelope
* @param envelope
* @return the geohash as a string
*/
public static String containingGeohash(Envelope2D envelope){
return "";
int lonBitsSize = (int) Math.ceil(geoHash.length() * 5 / 2.0);
int latBitsSize = geoHash.length() * 5 - lonBitsSize;

double lat = -90;
double latPrecision = 90;
for (int i = 0; i < latBitsSize; i++) {
if (((1 << (latBitsSize - 1 - i)) & latBits) != 0) {
lat += latPrecision;
}
latPrecision /= 2;
}

/**
*
* @param envelope
* @return up to four geohashes that completely cover given envelope
*/
public static String[] coveringGeohash(Envelope2D envelope){
return new String[]{};
double lon = -180;
double lonPrecision = 180;
for (int i = 0; i < lonBitsSize; i++) {
if (((1 << (lonBitsSize - 1 - i)) & lonBits) != 0) {
lon += lonPrecision;
}
lonPrecision /= 2;
}

return new Envelope2D(
lon,
lat,
lon + lonPrecision * 2,
lat + latPrecision * 2
);
}

/**
* Computes the geohash that contains a point at a certain precision
* @param pt A point represented as lat/long pair
* @param characterLength - The precision of the geohash
* @return The geohash of containing pt as a String
*/
public static String toGeohash(Point2D pt, int characterLength) {
if (characterLength < 1) {
throw new InvalidParameterException(
"CharacterLength cannot be less than 1"
);
}
int precision = characterLength * 5;
double lat = pt.y;
double lon = pt.x;

String latBitStr = Geohash.convertToBinary(
lat,
new double[] { -90, 90 },
precision
);

String lonBitStr = Geohash.convertToBinary(
lon,
new double[] { -180, 180 },
precision
);

StringBuilder interwovenBin = new StringBuilder();
for (int i = 0; i < latBitStr.length(); i++) {
interwovenBin.append(lonBitStr.charAt(i));
interwovenBin.append(latBitStr.charAt(i));
}

return Geohash
.binaryToBase32(interwovenBin.toString())
.substring(0, characterLength);
}

/**
* Computes the base32 value of the binary string given
* @param binStr Binary string with "0" || "1" that is to be converted to a base32 string
* @return base32 string of the binStr in chunks of 5 binary digits
*/

public static String binaryToBase32(String binStr) {
StringBuilder base32Str = new StringBuilder();
for (int i = 0; i < binStr.length(); i += 5) {
String chunk = binStr.substring(i, i + 5);
int decVal = Integer.valueOf(chunk, 2);
base32Str.append(base32.charAt(decVal));
}
return base32Str.toString();
}

/**
* Converts the value given to a binary string with the given precision and range
* @param value The value to be converted to a binString
* @param r The range at which the value is to be compared with
* @param precision The Precision (number of bits) that the binary string needs
* @return A binary string representation of the value with the given range and precision
*/

public static String convertToBinary(
double value,
double[] r,
int precision
) {
StringBuilder binString = new StringBuilder();
for (int i = 0; i < precision; i++) {
double mid = (r[0] + r[1]) / 2;
if (value >= mid) {
binString.append("1");
r[0] = mid;
} else {
binString.append("0");
r[1] = mid;
}
}
return binString.toString();
}

/**
* Compute the longest geohash that contains the envelope
* @param envelope
* @return the geohash as a string
*/
public static String containingGeohash(Envelope2D envelope) {
return "";
}

/**
*
* @param envelope
* @return up to four geohashes that completely cover given envelope
*/
public static String[] coveringGeohash(Envelope2D envelope) {
return new String[] {};
}
}
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