  While supernova remnants (SNRs) are widely thought to be powerful cosmic-ray
accelerators, indirect evidence comes from a small number of well-studied
cases. Here we systematically determine the gamma-ray emission detected by the
Fermi Large Area Telescope (LAT) from all known Galactic SNRs, disentangling
them from the sea of cosmic-ray generated photons in the Galactic plane. Using
LAT data we have characterized the 1-100 GeV emission in 279 regions containing
SNRs, accounting for systematic uncertainties caused by source confusion and
instrumental response. We have also developed a method to explore some
systematic effects on SNR properties caused by the modeling of the interstellar
emission (IEM). The IEM contributes substantially to gamma-ray emission in the
regions where SNRs are located. To explore the systematics we consider
different model construction methods, different model input parameters, and
independently fit the model components to the gamma-ray data. We will describe
this analysis method in detail. In the First Fermi LAT SNR Catalog there are 30
sources classified as SNRs, using spatial overlap with the radio position. For
all the remaining regions we evaluated upper limits on SNRs' emission. In this
work we will present a study of the aggregate characteristics of SNRs, such as
comparisons between GeV and radio sizes as well as fluxes and spectral indexes
and with TeV.
