The Dwingeloo 25 m telescope has recently surveyed the Galactic H I emission in the northern sky at angular resolution and 1 km/s spectral resolution. The key feature of the Dwingeloo survey is that the spectra have been corrected for stray radiation, which can account for up to half the signal seen at high latitudes. The DRAO interferometer is currently engaged in a survey of the H I in the Galactic plane at resolution. However, DRAO is limited to observing only the northern part of the plane.
VLA D configuration mosaics of Galactic H I emission reveal very complicated filaments and structures on all spatial scales. After only a few minutes integration per pointing in the D configuration, the image quality is limited by the effects of the incomplete Fourier plane coverage. This is a strong argument for the E configuration, which has essentially complete Fourier plane coverage in a single snapshot. E configuration mosaicing will permit much higher quality images of the complex H I structure, permitting deeper integrations.
With the VLA E configuration, it will be possible to survey the H I in large parts of the plane rapidly at angular resolution and 0.5 km/s spectral resolution. We know from VLA D configuration Galactic H I imaging that 30-sec snapshots with the VLA E configuration will detect abundant interesting structure. The VLA E configuration would be able to image the complicated H I filaments in only one snapshot. A survey covering one quadrant and 10 deg in Galactic latitude would take only 120 hrs to complete.
A high resolution fully sampled survey of Galactic H I would provide an important database for i) modeling the gas dynamics in the Galaxy; ii) comparison with surveys of molecular gas and detailed modeling of the conversion between atomic and molecular gas in molecular clouds or photodissociation regions; iii) comparison with the features in the radio continuum, possibly allowing determination of the distance to the continuum features if the H I and the continuum are correlated, and iv) detailed interaction between the violent events in the disk, such as SNR, H II regions, and disk blowout events, and the H I.