The earth's magnetic field is not parallel with the ground. In some locations it can be pointing more down than across.

NOAA has a magnetic field calculator where you can enter you latitude and longitude. For example, I am located at approx 19deg S 147degE and the field is

North Comp    East Comp    Vertical Comp    Total magnitude
32,434.4 nT   4,280.6 nT   -36,035.1 nT     48,670.7 nT 

So the downwards strength is more than the other two combined for my location. I'm guessing the calculator will also show a very strong down component for your location.

Some other things to be aware of are that the LSM303DLHC magnetometer can have quite large offsets, up to the equivalent of 2 earth magnetic fields, and therefore requires calibration. Also hard and soft iron distortions can affect the readings.

Edit: Please see my answer here for methods to calibrate the sensor.

The earth's magnetic field is not parallel with the ground. In some locations it can be pointing more down than across.

NOAA has a magnetic field calculator where you can enter you latitude and longitude. For example, I am located at approx 19deg S 147degE and the field is

North Comp    East Comp    Vertical Comp    Total magnitude
32,434.4 nT   4,280.6 nT   -36,035.1 nT     48,670.7 nT 

So the downwards strength is more than the other two combined for my location. I'm guessing the calculator will also show a very strong down component for your location.

Some other things to be aware of are that the LSM303DLHC magnetometer can have quite large offsets, up to the equivalent of 2 earth magnetic fields, and therefore requires calibration. Also hard and soft iron distortions can affect the readings.

Edit: Please see my answer here for methods to calibrate the sensor.

The earth's magnetic field is not parallel with the ground. In some locations it can be pointing more down than across.

NOAA has a magnetic field calculator where you can enter you latitude and longitude. For example, I am located at approx 19deg S 147degE and the field is

North Comp    East Comp    Vertical Comp    Total magnitude
32,434.4 nT   4,280.6 nT   -36,035.1 nT     48,670.7 nT 

So the downwards strength is more than the other two combined for my location. I'm guessing the calculator will also show a very strong down component for your location.

Some other things to be aware of are that the LSM303DLHC magnetometer can have quite large offsets, up to the equivalent of 2 earth magnetic fields, and therefore requires calibration. Also hard and soft iron distortions can affect the readings.

The earth's magnetic field is not parallel with the ground. In some locations it can be pointing more down than across.

NOAA has a magnetic field calculator where you can enter you latitude and longitude. For example, I am located at approx 19deg S 147degE and the field is

North Comp    East Comp    Vertical Comp    Total magnitude
32,434.4 nT   4,280.6 nT   -36,035.1 nT     48,670.7 nT 

So the downwards strength is more than the other two combined for my location. I'm guessing the calculator will also show a very strong down component for your location.

Some other things to be aware of are that the LSM303DLHC magnetometer can have quite large offsets, up to the equivalent of 2 earth magnetic fields, and therefore requires calibration. Also hard and soft iron distortions can affect the readings.

Edit: Please see my answer here for methods to calibrate the sensor.