diff --git a/Makefile b/Makefile
index 3eaf150..94122ee 100755
--- a/Makefile
+++ b/Makefile
@@ -3,8 +3,8 @@
 
 all: wh1080_rf
 
-wh1080_rf: wh1080_rf.o bcm2835.o bmp085.o
-	$(CC) -lm wh1080_rf.o bcm2835.o bmp085.o -o wh1080_rf
+wh1080_rf: wh1080_rf.o bcm2835.o bmp085.o wunderground.o
+	$(CC) -lm wh1080_rf.o bcm2835.o bmp085.o wunderground.o -o wh1080_rf
 
 wh1080_rf.o: wh1080_rf.c
 	$(CC) $(CFLAGS) wh1080_rf.c
@@ -15,5 +15,8 @@
 bmp085.o: bmp085.c
 	$(CC) $(CFLAGS) bmp085.c
 
+wunderground.o: wunderground.c
+	$(CC) $(CFLAGS) wunderground.c
+
 clean:
-	rm -f wh1080_rf.o bcm2835.o bmp085.o wh1080_rf
\ No newline at end of file
+	rm -f wh1080_rf.o bcm2835.o bmp085.o wunderground.o wh1080_rf
diff --git a/wh1080_rf.c b/wh1080_rf.c
index cdeb2e8..905f0d5 100755
--- a/wh1080_rf.c
+++ b/wh1080_rf.c
@@ -50,6 +50,7 @@
 #include "wh1080_rf.h"
 #include "bcm2835.h"
 #include "rfm01.h"
+#include "wunderground.h"
 
 uint16_t bw_scale[6] = {BW_67, BW_134, BW_200, BW_270, BW_340, BW_400};
 
@@ -178,13 +179,18 @@
 	return duty;
 }
 
+// pressure function and value
 extern int read_bmp085(float altitude);
+extern float pressure_hpa;
 
 int main(int argc, char *argv[])
 {
 	//unsigned char bytes2[] = {0xa1,0x82,0x0a,0x59,0x03,0x06,0x00,0x4e,0x06,0xc8};
 	//calculate_values(bytes2);
 	//return -1;
+
+	// initialize weather underground module
+	WUnderground_Init();
 	
 	uint8_t packet_sig = 0xfa;
 
@@ -433,7 +439,7 @@
 					read_bmp085(ALTITUDE_M);	// read pressure, calculate for the given altitude
 					#endif
 					
-					calculate_values(bytes);
+					calculate_values(bytes, pressure_hpa);
 					
 					// Wait for remainder of 47 seconds in standard scheduler until we can expect the next read
 					scheduler_standard();
@@ -470,7 +476,7 @@
 
 char *direction_name[] = {"N", "NNE", "NE", "ENE", "E", "ESE", "SE", "SSE", "S", "SSW", "SW", "WSW", "W", "WNW", "NW", "NNW"};
 
-void calculate_values(unsigned char *buf) {
+void calculate_values(unsigned char *buf, float pressure_hpa) {
 	
 	unsigned short device_id = ((unsigned short)buf[0] << 4) | (buf[1] >> 4);
 	unsigned short temperature_raw = (((unsigned short)buf[1] & 0x0f) << 8) | buf[2];
@@ -498,6 +504,10 @@
 	printf("Wind speed: %0.2f m/s, Gust Speed %0.2f m/s, %s\n", wind_avg_ms, wind_gust_ms, direction_str);
 	printf("Wind speed: %0.1f mph, Gust Speed %0.1f mph, %s\n", wind_avg_mph, wind_gust_mph, direction_str);
 	printf("Total rain: %0.1f mm\n", rain);
+        printf("Pressure (sea level): %0.1f hpa\n", pressure_hpa);
+
+	// submit observation to weather underground
+	WUnderground_Observation(temperature, humidity, wind_avg_mph, wind_gust_mph, direction_str, rain, pressure_hpa);
 }
 
 /*
diff --git a/wh1080_rf.h b/wh1080_rf.h
index 17e4980..3371cff 100755
--- a/wh1080_rf.h
+++ b/wh1080_rf.h
@@ -1,8 +1,8 @@
 
 //#define USE_BMP085
 //#define ALTITUDE_M	210.0f
-#define ALTITUDE_M	10.0f
+#define ALTITUDE_M	6.0f
 
 void scheduler_realtime();
 void scheduler_standard();
-void calculate_values(unsigned char *buf);
+void calculate_values(unsigned char *buf, float pressure_hpa);
diff --git a/wunderground.c b/wunderground.c
new file mode 100644
index 0000000..0e277fa
--- /dev/null
+++ b/wunderground.c
@@ -0,0 +1,99 @@
+/* Module for uploading observations to Weather Underground
+  (C) britishideas.com
+  GPL V2 - see license.txt */
+
+#include <stdio.h>
+#include <string.h>
+#include <math.h>
+#include "wunderground.h"
+
+// file that contains weather underground station ID (first line) and
+// password (second line)
+#define CREDENTIALS "wunderground_creds.txt"
+
+// API url
+#define WUURL "http://rtupdate.wunderground.com/weatherstation/updateweatherstation.php"
+
+// maximum lengths of station id and password
+#define STATIONIDLENGTH 50
+#define PASSWORDLENGTH  50
+// maximum command length
+#define CMDLENGTH 1024
+
+// module variables
+static char gStationId[STATIONIDLENGTH];
+static char gPassword[PASSWORDLENGTH];
+
+// initializes the module
+void WUnderground_Init
+  (
+  void
+  )
+{
+  // fixme - read station id and password from credentials file
+  strcpy(gStationId, "IHORNSEA3");
+  strcpy(gPassword,  "LIA80RvnuUY8WpO3peGC");
+}
+
+// submits an observation
+void WUnderground_Observation
+  (
+  double TemperatureC,                   // temperature in C
+  double Humidity,                       // as a percentage
+  double WindAveMph,
+  double WindGustMph,
+  char *WindDirection,                   // string "N", "NNE", "NE", "ENE", "E", etc.
+  double TotalRainMm,                    // total since battery change
+  double PressureHpa                     // pressure at sea level
+  )
+{
+  char Cmd[CMDLENGTH];
+  char UTCTimestamp[20];
+
+  // get temperature in F
+  double TemperatureF = (TemperatureC * 9.0 / 5.0) + 32.0;
+
+  // calculate dew point in F
+  // see: http://www.gorhamschaffler.com/humidity_formulas.htm
+  double Es = 6.11 * pow(10.0, 7.5 * TemperatureC / (237.7 + TemperatureC));
+  double E = Humidity * Es / 100.0;
+  double Tdc = (-430.22 + 237.7 * log(E)) / (-log(E) + 19.08);
+  double DewPointF = (Tdc * 9.0 / 5.0) + 32.0;
+
+  // get wind direction
+  double WindDegrees = 0;
+       if (!strcmp(WindDirection, "N"))   WindDegrees = 0;
+  else if (!strcmp(WindDirection, "NNE")) WindDegrees = 22.5;
+  else if (!strcmp(WindDirection, "NE"))  WindDegrees = 45;
+  else if (!strcmp(WindDirection, "ENE")) WindDegrees = 67.5;
+  else if (!strcmp(WindDirection, "E"))   WindDegrees = 90;
+  else if (!strcmp(WindDirection, "ESE")) WindDegrees = 112.5;
+  else if (!strcmp(WindDirection, "SE"))  WindDegrees = 135;
+  else if (!strcmp(WindDirection, "SSE")) WindDegrees = 157.5;
+  else if (!strcmp(WindDirection, "S"))   WindDegrees = 180;
+  else if (!strcmp(WindDirection, "SSW")) WindDegrees = 202.5;
+  else if (!strcmp(WindDirection, "SW"))  WindDegrees = 225;
+  else if (!strcmp(WindDirection, "WSW")) WindDegrees = 247.5;
+  else if (!strcmp(WindDirection, "W"))   WindDegrees = 270;
+  else if (!strcmp(WindDirection, "WNW")) WindDegrees = 292.5;
+  else if (!strcmp(WindDirection, "NW"))  WindDegrees = 315;
+  else if (!strcmp(WindDirection, "NNW")) WindDegrees = 337.5;
+
+  strcpy(UTCTimestamp, "timestampgoeshere");
+
+  sprintf(Cmd, "wget -b -a /tmp/wunderground.log -O /tmp/wunderground-result.html \"%s?action=updateraw&ID=%s&PASSWORD=%s&realtime=1&rtfreq=48&dateutc=%s&tempf=%f&humidity=%f&windspeedmph=%f&windgustmph=%f&baromin=%f,&dewptf=%f&winddir=%.1f\"",
+    WUURL,
+    gStationId,
+    gPassword,
+    UTCTimestamp,
+    TemperatureF,
+    Humidity,
+    WindAveMph,
+    WindGustMph,
+    PressureHpa * 0.0295299830714,
+    DewPointF,
+    WindDegrees
+    );
+
+  printf("%s\n", Cmd);
+}
diff --git a/wunderground.h b/wunderground.h
new file mode 100644
index 0000000..f8971af
--- /dev/null
+++ b/wunderground.h
@@ -0,0 +1,27 @@
+/* Module for uploading observations to Weather Underground
+  (C) britishideas.com
+  GPL V2 - see license.txt */
+
+#ifndef _WUNDERGROUNDH_
+#define _WUNDERGROUNDH_
+
+// initializes the module
+extern void WUnderground_Init
+  (
+  void
+  );
+
+// submits an observation
+extern void WUnderground_Observation
+  (
+  double TemperatureC,                   // temperature in C
+  double Humidity,                       // as a percentage
+  double WindAveMph,
+  double WindGustMph,
+  char *WindDirection,                   // string "N", "NNE", "NE", "ENE", "E", etc.
+  double TotalRainMm,                    // total since battery change
+  double PressureHpa                     // pressure at sea level
+  );
+
+#endif // _WUNDERGROUNDH_
+