After connecting the navboard I was wondering what are the units of the tilt sensor and compass output and how the functions handle negative tilt. Also the compass command '$C' has been sending back the same output, 6553, regardless of the orientation of the srv-1.  
 
The current setup on the breakout board is as follows:
 
TP => TMR3
RX => UART1_RX
TX => UART1_TX
GND => I2C_GND
3.3V => I2C_3.3V
SDA => I2C_SDA
SCL => I2C_SCL
 
Any help would be greatly appreciated.

int compass_inited = 0;
void read_compass() {
    unsigned char i2c_data[12];
    short ix, i, head, pitch, roll;
    unsigned char addr;
 
    // HMC5843
    addr = 0x1E;
    if (compass_inited == 0) {
     i2c_data[0] = 0x00; i2c_data[1] = 0x20; i2cwrite(addr, (unsigned char *)i2c_data, 2, SCCB_ON);
     i2c_data[0] = 0x01; i2c_data[1] = 0x20; i2cwrite(addr, (unsigned char *)i2c_data, 2, SCCB_ON);
     i2c_data[0] = 0x02; i2c_data[1] = 0x00; i2cwrite(addr, (unsigned char *)i2c_data, 2, SCCB_ON);
     delayMS(10);
     compass_inited = 1;
    }
    for(i = 0; i < 6; i++) i2c_data[i] = 0x00;
    i2c_data[0] = 0x03;
    i2cread(addr, (unsigned char *)i2c_data, 6, SCCB_ON);
    head = ((short) (i2c_data[0] * 256 + i2c_data[1]));
    pitch = ((short) (i2c_data[2] * 256 + i2c_data[3]));
    roll = ((short) (i2c_data[4] * 256 + i2c_data[5]));
    printf("##C x=%d y=%d z=%d [%d %d %d %d %d %d]\r\n", head, pitch, roll,
     i2c_data[0], i2c_data[1], i2c_data[2], i2c_data[3], i2c_data[4], i2c_data[5]);
}

Thanks the code worked when I recompiled the firmware, I was wondering if I could use the same code to create a function in the picoc library? Also from the source it says that the y axis is pitch however it varies greatly when the heading of my SRV-1 changes. I don't really understand why the pitch would change with the heading changes while driving the SRV on a flat surface. Thanks for your help.

Andrey's changes have been added to the latest firmware -  
    http://code.google.com/p/surveyor-srv1-firmware/downloads/list
 
The "$c" command accesses the HMC5843 raw data, though we still need to add some code to compute an actual heading.